What are your expectations for weather? Reason why I ask is because Mt Rainier will have likely have heavy snow in April and probably heavy rain in May. Not all parts will be open, either. As an example, the visitor center at Paradise will likely only be open on weekends in April before it is open during week in May.

This might help.

http://www.nps.gov/mora/planyourvisit/index.htm

beanweb, good point about the weather and I appreciate your response and the link. I assumed that the area gets quite a bit of rain year round, but I never even considered heavy snowfalls. So if we were targeting spring (lets say early May), should we just stay somewhere near Seattle and make day trips?

Look at Port Townsend for your Olympic Peninsula location. You can do day trips to Olympic National Park but be based in an historic Victorian seaport with a choice of hotels, BnBs and restaurants. You can take ferries over which your girls would probably love. Seattle is a great city and a combo of these two would give you a nice sample.

In April and May there is still much snow in the mountains, but not in Seattle.

In the time you have, after a day or two in Seattle, I would go to San Juan Island (my favorite) or Orcas Island for two days. From, there I would drive to Whidbey Island and take the ferry from Coupeville to Port Townsend and spend a couple days on the Olympic Peninsula.

Port Townsend is a delightful little town, but it is not conveniently located for visiting Hurricane Ridge, Marymere Falls, Neah Bay, the Hoh Rainforest, etc. Port Angeles or Forks would be better for that.

HTtY

PS July and August are our summer months.

Go to www.weatherbase for historical data. It does NOT rain year round. We just went 82 days without measurable precipitation, but have to admit that this has been an unusual year. As HTTY indicates, the later in the spring you can visit, the better.

I think that Rainier is best when the flowers are blooming. The flowers their are the best of anywhere I've ever been. August for that. It would be a shame to miss them, IMOP.

We really loved Whale Watching with James Maya this past August in the San Juan Islands.

Olympics are great, but the Mountain area would probably be closed still for snow. Olympics are kinda like 3 parks in 1. The main hikes at Hoh, Sol Duc falls, and the beaches are all easy and short. So, your 3 year olds could probably handle them just fine. They would probably like to tidepool at Rialto Beach down to Hole in the Wall thru the sand.

Any chance you could put this trip off until then?
Go ahead and get your lodging asap if you are staying at Paradise Lodge or any of the lodges in Olympic National Park.

Here is a link to our photos from July and August this year.
http://share.shutterfly.com/action/welcome?sid=0IatW7FqybsWgh

This year there was still around 7-8 feet of snow on the ground at the Paradise visitors center on Mount Rainier on July 1. In April/May, higher elevations in Mount Rainier NP and Olympic NP (such as Hurricane Ridge) will most likely still be snow-covered. The access roads might be plowed or clear, but driving might be tricky.

The coast and rain forest valleys on the Pacific side of the Olympic Peninsula will be quite wet, but that's no reason not to visit. In the spring the coast can be spectacular - waves crashing on rocks, etc., and the rain forest valleys (Hoh and Quinault) are eerie/spooky, as the (huge) resident Roosevelt Elk have eaten much of the undergrowth over the winter, leaving surprisingly long vistas under the tree canopy - moss underfoot, big trees and hanging Spanish moss vanishing into the mist overhead. Gorgeous, but it WILL be wet.

With a week personally I'd focus on the northeastern tip of the Olympic Peninsula, around Port Townsend, or on Whidbey Island. The benefits of this area are (a) it's possible (around 2 hours) to do a day trip out to the coast or Hoh Valley, while (b) the area itself is shielded from the wettest weather by the Olympic Mountains (it's in the "rain shadow" of the Olympics.) And (c) - in late April or early May (could be mid-April, hard to say) the Skagit Valley - on the mainland just to the east of the Olympic Peninsula - will be in stunning bloom, with the largest concentration of tulip fields outside Holland, daffodils before that, and some hundreds of thousands of Snow Geese hanging out in the fields. For visitors and kids, it's fantastic. A couple of pictures -

Daffodils - http://gardyloo.us/DSC_0077c.jpg
Tulips - http://gardyloo.us/tulips404%20025s.jpg
Geese - http://gardyloo.us/20100319_56as.jpg (Mount Baker behind)

Whidbey Island is terrific - from beautiful and impressive Deception Pass in the north, down to the cute waterfront villages of Coupeville (mid-island) and Langley at the south end... beaches, a marvelous Rhododendron "reserve," a great state park near the ferry dock, great for beachcombing... it's got it all.

So one possible plan would be to spend maybe four days around Whidbey or Port Townsend (a very cute historic town with many wonderful Victorian buildings) and three or so in Seattle itself.

Now having said that, I'd also suggest quite a big alternative - visit the Columbia Gorge (just east of Portland, Oregon) instead.

In my view, spring is the best time to visit the Gorge. In terms of weather, it gets drier and warmer the farther east you travel, so if the rain becomes oppressive you just jump in the car and an hour later the sun is out. (The Cascades stop the rain, just like the Olympics.)

But the Gorge itself is fabulous then... there are a string of waterfalls along the Oregon side of the Gorge that will be awesome in the spring (with snow melt runoff) and the many orchards around Hood River and the Hood River Valley will be in full bloom. The road to Timberline Lodge on Mount Hood will probably be clear, even if they're still skiing at the lodge itself (so at least a "snow trip" for the kids) and the windsurfers will probably be cheek-by-jowl in Hood River (self-proclaimed windsurfing capital of the USA.)

At the hatchery next to the Bonneville Dam (near Cascade Locks) the kids (and their pet adults) can see the amazing, huge Columbia River sturgeon that have been impressing kids for generations; you can visit the surprising Maryhill Museum on the Washington side near The Dalles... in short, it's a fantastic destination, and a week is perfect. (Oh, and if you need a city fix for a day or two, Portland is no slouch on that front.)

More pictures:

Vista House on the Gorge Highway - http://gardyloo.us/20100509_5a.jpg
Mount Hood from the Hood River Valley - http://gardyloo.us/20100509_85a.jpg
Latourelle Falls on the Oregon side - http://gardyloo.us/latourellefallshdr1.jpg
Mount Hood from Portland - http://gardyloo.us/20100510_21b.jpg

Hope this doesn't just create confusion. It's a great time to visit both areas.

Thank you all so much for your replies! You've helped a lot! I enjoyed all of the pictures and they've aided in helping me understand the area easier. I'm in the very beginning stages of planning so I sheepishly admit that I never even heard of some of the names so you've given me something to start with.

gardyloo, the flower pictures are stunning! But...now I want to go to Mount Hood too! Flight prices seem to be very similar to both Seattle and Portland from Charlotte so I could possibly consider flying into one city and out of the other. And I could move the trip back to the summer months if necessary. We are used to traveling during off-peak season (cheaper prices, typically, at least in Europe) and dealing with some less-than-stellar weather. Of course we've never done it with children in tow so it's something to consider.

Superb info. I am planning a week (in two weeks) just around Seattle but the two of us will be going to the state for two weeks net September.

Can anyone provide some insight into the above activities as they would be in September?

September is usually quite beautiful in Seattle and the rest of Washington. Here the average high is 70 F. and average rainfall is about one inch.

HTtY

Coming all the way from Charlotte, and with a pair of 3yo's in tow, are the central factors involved in planning such a trip.

Were it a pair of adults, then the endless car travel implied in most cases of such visits would be sensible, but you just need a better, and more simple strategy.

There's just... much more to do for children, to keep them entertained, in the central-ish Seattle region than is the case with outlying communities.

It wouldn't be too difficult to fly to Seattle, take the efficient new "Link Light Rail" into the center of town, rent a hotel room there for 2 or 3 days and then exhaust many of the area tourist spots (Pike Place Market, Seattle Center {park-like area that is home to the Space Needle - not merely the 'center of town'}, Aquarium, etc.).

(only) THEN, for the next leg of your trip, rent a vehicle from a downtown location and jump aboard a ferry across Puget Sound for at least some sort of a circuit of the Olympic Peninsula. Stay out there for a night or two, and then maybe circle around via Olympia and toward Mount Rainier from there. (perhaps choosing "Paradise" for a visit before circling around the east side of the mountain)

After that you'd be ready to make your way to SeaTac airport for your flight home. (IF it saves major $$$ with the rental car, it could even work that one of you stays with the kids (perhaps even at a hotel near the airport) while the other returns the car at the same downtown location from which you got it, before returning to the airport via the convenient light rail)

Of course there are many more possibilities, perhaps the best of which involve far too much car-travel time to best suit 3yo's, but I sense that you'll quickly pick-up on major differences in nature between Seattle and Charlotte soon after arrival here, and EVEN IF restricted to the downtown area for the first two or three days.

Absorbing as much as you can when so far from home makes the most sense, but perhaps not as much when needing to keep 3yo's content and intrigued during the process.

Here's a link to my trip report of Seattle from a few years ago. It is of the main sites for kids:

http://www.fodors.com/community/united-states/trip-report-seattle-area-in-july-with-kids.cfm

We have done the Seattle Aquarium on another trip and it is also quite decent although we like the one at Newport OR better. If you go to the Seattle Aquarium, be sure not to miss the sea horses and the sea dragons.

Also, note, in our trip report, we chose to go to the Pacific Science Center rather than the Children's Museum. Both have a lot for young kids, so you can't go wrong. But, they are two different museums a block apart.

I forgot to mention that I wouldn't try doing both Portland and Seattle areas with young children. I think it would be too much driving to enjoy things.