If you will have a rental car you can easily get to Mount Vernon by car from Chantilly or about anywhere else in the DC metro area.

For that matter you could stop off at Mount Vernon on the way from Richmond if you are willing to leave early enough but BEWARE of I-95 north on a weekday morning and yes as early as 5-5:30 AM, especially between Fredericksburg and the bottom of the Beltway I-495.

Philadelphia is very easy to find your way around in and there are many things to do; let us know your interests and we (the Philadelphia crew here ) can give you lots of directions, advice, and tours you can take on your own. You could do an entire cheesesteak tour, of course, but there are so many other wonderful things to eat that you might want to branch out a bit.
Here's one example of some of the things you can do: http://www.fodors.com/community/united-states/advice-on-philadelphia-itinerary.cfm (Note: Franklin Court museum is closed for renovation, the Atwater Kent is now the Philadelphia History Museum--and a great place, too!--and Naked Chocolate, alas, is no more. But Capogiro is still there!)

Lancaster can be done as a long day trip from Philadelphia, and for me that would be enough (combined, perhaps, with a visit to the Reading Terminal Market somewhere between Wednesday and Sunday.) I'd suggest Landis Valley Open Air Museum http://www.landisvalleymuseum.org/ for a historic overview of the Pennsylvania Germans, but, well, the Amish are just living there, not really a tourist attraction.

I'd book one ("Old City" area, preferably) place for Philadelphia and one for Washington if I were you; Washington can be rather wearing with the long distances between things. There's a great walking tour of Washington, free except for tip, http://www.freetoursbyfoot.com/dc/ Might help you in getting a good overview.

Happy planning!

> observe the Amish way of life in Lancaster

The first thing to be aware of: 90% of what you will find in Lancaster not only has nothing whatsoever to do with the Amish way of life, but is in direct opposition to it. You CAN get a glimpse of this life-style, but it takes effort.

If the next two paragraphs are simply preaching to the choir, then great. But these things need to be said.

The second thing to be aware of: the Amish has spent almost three centuries trying to remain isolated from "the English" (their term for outsiders) and have no interest in sharing their story with them. You will easily be able to meet Amish folks selling you products, but that's all you're going to be able to observe. Do NOT ask them questions about their choice of life, and **DO NOT** take photos of them -- not even from a distance.

There are very limited tours of the area that delve a little deeper into this group, conducted by knowledgeable people who are not Amish themselves. This is most likely as much info.

Thanks so much for the suggestions. Good to know what to do/not do/expect/not expect about the Amish people. We don't want to offend; we're just interested. We will have our own car. We want to plan based on the weather being cold, windy, rainy, etc., so probably no walking tours unless it turns out to be beautiful weather and we can schedule one at the last minute. Can we do this in Philly and WDC? We enjoy historical sights and also "known by locals only" off the beaten path places of interest, places to eat, etc. We've never had a Philly Cheesesteak, and we're not big eaters, but we want to eat one at someplace famous for theirs. I forgot to mention that we also want to see Gettysburg battlefield while in PA. Any tips on best day of week to go, hours, etc.? I'm wondering if they have an audio tour you can play in your car while driving through the park? Should I post a separate inquiry about this? Thanks again for all your tips.

The self-audio tour of Gettysburg is the way to go. The CD is sold at several shops in the town; not sure if you can buy it on the battlefield grounds. As for days/hours, avoid the weekend if you can. You obviously would want to combine that with your trip to Lancaster, as they are in the same general direction. Again, in Lancaster, avoid the weekend if possible.

The historic area in Phila is compact and walkable. Main sights: Liberty Bell, Independence Hall, Constitution Center. From that area, you can take a horse-drawn tour. Hard to predict the weather in March, but it could be OK.

Best cheese steak? You trying to start a fight? (LOL) Pat's or Geno's in South Philly are the traditional spots, but really, you want to go to the Reading Terminal Market and eat a roast pork sandwich with broccoli rabe and provolone at DiNic's. Plus, the Market is worth a visit.

Best restaurant local eat at: Scannicchio's at Broad and Porter.

For Philadelphia...check out these sites:
http://www.visitphilly.com/?gclid=CJ-piJnbg7UCFc1lOgodXTwAkg
http://www.uwishunu.com/?gclid=CM2Qrarbg7UCFe47Ogod6TwAyw
Lots of info on what to see and do.
Go to the Visitors' Center first and get a free timed ticket to do the tour of Independence Hall. You can also get maps a great info at the center.

I just saw this thread, but I will post this in case you are still checking. Since you will have a car, I would drive to Philly for at least 2 nights then drive to York PA for Gettysburg and Amish for at least 2 nights then on down to DC for at least 2 nights. You still have extra nights, but as you get more into planning I am sutre you will be able to fill them up.

MT Vernon can be visited on the way up or back...you will really want about 4 hours to see it all, try to not be there on the weekend...I usually get there after lunch and the crowds are thinning.

Can't help with in Philly.

But we just did a short trip to Gettysburg and the Amish country...you might like to check out our time there this past Oct. We were coming down from NY on the way back to TX. We are in our late 60's and I walk with aid of canes.

I did a day by day blog of the extended trip..we were in that area Oct 4,5 & 6, 2012.

Go to www.landscruise2012.blogspot.com then scroll down to the botton for the index and click on Oct 4. It will give you an idea of what can be done in two full days in the area. I love that part of the US.

We stayed at the Homewood Suites (our travel hotel of choice) in York, PA and I think it was about $119 a night. If you stay M-Th nights the rate includes a nice simple supper along with the regular hot breakfast and is a great value. This was actually one of the nicest HW suites we have stayed in and is well located for the whole area.

You probably need at least one night in the area though 2 nights coming from Philly on the way to DC would be enough to enjoy both Gettysburg and the Amish area. I wouldn't mess with Lanscaster unless you have extra time, instead spend time driving the country lanes and stop in the small towns (See blog) to shop or just get something to drink. You need a full day that Gettysburg and York is close enough for that. Yes, you can get the audio tape tour at the visitors center as well as a Nat Park tour booklet, if you don't want to buy the audio one.

I was in DC with my granddaughter in March 2012. Stay in one of the downtown hotels, close to the Mall as you can afford. I like the Marriott or the Willard...I have gotten really great prices on weekends at both. My Granddaughter and I (canes and all) walked to many of the sites from the hotel. When I tired, we hailed a taxi from site to site or hotel for as little as $5 to $10. I have taken 4 of my grandchildren so far with #5 going this summer and I plan for 3 nights, two full days and can really see a lot.

The first time I took a grandchild we stayed in Alexanderia (but also a great location especially the Embassy Suites, right at the train station) and rode the train in. This is a great way to go if you are have young legs, but I found all the metro steps very tiring and didn't have much left for the sights. Having a close by hotel really helped us, If I got tired we just went back to the hotel for a rest and then hit the road again. Easy to do when you are staying close by.

Do the monuments by moonlight tour or better yet just walk the Mall from the Capitol to the Lincoln M at sun set. It is down hill and a beautiful walk. I made it to the WWI Memorial then we took a taxi to the Lincoln M. Driver dropped us off and gave us ~30 mins and his cell # to call to pick us up and take us back to Hotel...$20!

You could not pay me enough money to try to drive in DC. We took a tour bus from Williamsburg in 2003, which was the way to go. The traffic was BRUTAL for the driver. We saw a lot that way, despite only spending up to a half-hour or one hour in one place. It was pretty amazing for $50 pp.
Philly can be daunting driving in, too. We drove and spent 45 minutes in one spot crossing the bridge from NJ after 10 a.m. on a Friday. We reluctantly returned the next day, and to our surprise, it looked much like a ghost town. We drove right in, parked in the same parking lot (for free this time) and saw a lot more than we did the day before. It also seems like, in some spots, there are three lanes of traffic jammed on two-lane streets. But the trip there was pretty amazing. Saw a lot.

Re Lancaster, PA and PA Dutch Country, here's something I posted on a previous thread, slightly modified:

"Lancaster is a pleasant city with very attractive architecture (a walking tour is possible) and some nice attractions, some of which I have experienced (Central Market, Lancaster Quilt and Textile Museum, Amish Farm and House) and some of which I haven't (Wheatleigh, plus some attractions outside of Lancaster such as Ephrata Cloister, Landis Valley Museum, Hans Herr House, and such). Eating at a PA Dutch style eatery can also be enjoyable (I went to Good and Plenty, which was much enjoyed). You're also not far from Hershey, Harrisburg, and Gettysburg, all worthwhile places to experience to varying degrees. There are to be sure a significant number of strip malls and some attractions which sound a bit cheesier that can be found here. And I've seen the gripes from folks on this board who just hate the whole area and unilaterally dismiss it. Having experienced (and enjoyed) a respectable amount of what this area has to offer, I'm not one to say "stay away." The good is well worth experiencing, and the bad can be minimized with some research."

Re Philly cheesesteaks, I've had them at several places, and here's how I'd rank them: Jim's, Cosmi's Deli, Rick's, Tony Luke's (ballpark), Dolce Carini, Campo's, Sonny's, Pat's, Geno's. The last two are among those most often mentioned, but I'd put them dead last among those I've tried and I can't recommend either. Have not had those at Tony Luke's main location, John's Roast Pork, Lazaro's, or at two Manayunk spots, Chubby's or D'Alessandro's.

Definitely get a roast pork sandwich as well. The one at DiNic's is excellent (have had this one), and reportedly the one at John's is as well (haven't had theirs).