Another part-day trip from Traverse City (I never got excited about that town either) is the Leelanau Peninsula. Drive along the shore of the bay up to the state park at the north tip and see the little lighthouse there. A mile back south, there's more state park land where you can park and walk west (maybe 3/4 mile?) to a beach. Drive around inland in the peninsula and see rolling hills with dairy farms and orchards. This SP has a CG but it's rustic with small sites, and I think there might only be one or two (if that) which your rig could fit into.
There is a paved hike/bike trail from Charlevoix to Petoskey. There's a long trail along the MN shore, too.
I should have mentioned, at the Porcupine Mountains SP there's a hiking trail along Superior between the east and west units for serious backpackers, if you're into that; it take a couple of days to complete the journey.
Isle Royale is a great place for those who like wild nature. Most people tent, maybe canoe/kayak, and do serious hiking.
In Wisconsin, the Door County peninsula bills itself as the Cape Cod of the Midwest. Eat a fish boil. Peninsula SP is particularly nice for walking, biking, swimming, and enjoying the views. You can take a ferry to Washington Island if you like.
My brother tells me there are a couple of really good museums on the north side of Chicago.
