If you go across upper Michigan then down along the Lake Michigan shoreline, you can catch all four of the National Lakeshores in on trip.
Apostle Islands National Lakeshore
Pictured Rocks National Lakeshore
Sleeping Bear Dunes National Lakeshore
Indiana Dunes National Lakeshore
We just did a 3-week past October up from Indiana Dunes to as far as Pictured Rocks. We really enjoyed it but plan on going back in September one year so we can have better weather. If you like state parks, when you get to Michigan, pay the $32 for the annual park pass (exp end of year) as you will get it back if you spend five days in parks. Makes it really easy to stop and visit all the little parks along the coast.