Make a loop going all the way around Lake Michigan. You'll still get to Milwaukee and Door County on that trip. Madison and Wisconsin Dells aren't very far out of the way. Most things in Wisconsin Dells are going to be closed in October.

There is a great deal to see in the western part of the Michigan "thumb". The area between the dunes and Traverse City and Petoskey is very attractive.

I disagree that most things are closed in Door County in October--it's a beautiful time to visit and there are lots of events going on.

I said most things in Wisconsin Dells are closed, not Door County.

I apologize for making that mistake--totally my error.

What about the weather? does it rain a lot? Is it too cold?

Too cold for what?
hiking-not too cold
Swimming outdoors--too cold

October - varies a lot for temps, generally not real rainy.

I guess it depends on what sort of things you like to do and see. Door County is always one of my favorites. We often stop in Cedarburg, Kohler and some of the other smaller towns along our way as we travel north. We try to drive along Lake Michigan as much as possible because we enjoy the scenery.

One of the most overlooked areas is the Great River Road. Fourteen days should allow you plenty of time to visit that area as well. October is generally a great time to see the fall colors. It is quite scenic as one travels between the river and the bluffs. In addition the Mississippi is a major flyway for migrating birds. It's impressive to watch the eagles soar over the bluffs.

Wisconsin Dells is good if you like to gamble (there is an Indian Casino) or have children along who never tire of the water parks. There are spa services at some of the resorts as well. Other than that I feel much of the beauty has been stripped away by development.

Let us know what you are looking for and we may have better suggestions for you.

I forgot to mention that the weather in October can bring anything from snow to 80 degrees. The normal temps probably range in the 50's 60's. Wisconsin weather is always a gamble and it keeps us guessing.

Another vote for the Great River Road. I stopped last summer in Red Wing, Minn., just across the river and had a good time before driving down the Mississippi.

mdwest, we are couple, traveling alone. Casinos aren't in our plans. We prefer sightseeings.We also found a Lake Michigan Circle Tour. There is a tour crossing Lake Michigan by ferry. something about a 4 hours crossing time. is it cool? should we try it?

There's really nothing cool or scenic about the ferry. You're just out on the open water with nothing to look at.

It doesn't save you any time either if you're starting in Chicago. By the time you drive up to the ferry and cross, you'd be able to drive to the landing site in Michigan.

I haven't taken the ferry for years but I agree with WhereAreWe.
It was pretty boring. People around here take the ferry to avoid the drive down around the southern portion of Lake Michigan and all of the traffic congestion that entails.

The ferry is pretty expensive and I don't even know if it would be open in October. The route you suggested will be BEAUTIFUL in October (but I agree with other posters - October weather is extremely unpredictable, so pack layers!) and more than doable in 14 days. I've never done the Lake Michigan loop but I bet it would be beautiful as well, and the Great River Road is indeed gorgeous!! Here are a few of my suggestions, some a little off the beaten path but worth looking into

Holy Hill in Hubertus is a little out of the way if you're sticking to 43/94 but will absolutely be worth it in the fall. I haven't been back since I went with my parents many years ago but the views are spectacular, and it's a very wooded area which will look fantastic in fall colors!

Fall Fest in Sister Bay (Door County) is in October. If you plan on going up that way be sure to book your hotel early because this is a huge attraction! It's sort of a double-edged sword because Door County gets crazy busy during festival weekends and I prefer going up there when it's a little quieter, but for someone who's never been, it may be worth it to check it out.

New Glarus Brewery is located just southwest of Madison. If you're at all interested in beer I highly suggest taking a visit! They're open until 4pm most days, have self-guided tours for free and have super cheap tasting prices... it's up on this beautiful hill and it's just quaint and wonderful. Even if you don't get a chance to visit, be SURE to have a glass of Spotted Cow while you're in the state - New Glarus doesn't distribute outside of WI so get some while you have the chance

If you decide to go the Great River Road way, be sure to stop in Winona, MN, just a half hour outside of La Crosse! The drive will alone will be worth it (I can't say enough good things about fall colors) and it's full of cute coffee shops and outdoors activities. You can also take a drive up Garvin Heights for a lookout over the city and bluffs. Simply gorgeous. If you're interested in bird watching, make a quick drive up to Wabasha, MN and make a stop at the eagle center there. Bald Eagles LOVE this area of the country and it's a very fun and educational place to stop!

These posts also have fantastic ideas for food and sightseeing throughout Wisconsin
http://www.fodors.com/community/united-states/wisconsin-wanderings.cfm
http://www.fodors.com/community/united-states/fall-leaves-in-wisconsin.cfm

Hope this helps! I could go on and on but I'll stop for now - let us know if you want any other suggestions when your narrow down your itinerary!