Indiana and Michigan

The Frederick Meijer Gardens on the east side of Grand Rapids is a well worth while stop. Check their website Link for more info.

Dave

in addition to what Chezmoose said, Fort Wilkins State historic park and Fayette state HP are both really good. Porcupine mountain area also. Glass bottom boat tours in Alpena on east side are very nice also, national shipwreck preserve. St Ignace also. Michigan really has a lot to see. As said by someone else, the Indiana dunes area is also very neat. Enjoy the travels around the state. Hope this may help, Happy trails Bert.

Traverse City and Petosky are central to some great areas. Travis Bay TV resort and Hearthside in Petosky are two fo our favorites.

We stayed at Indigo Bluffs in MI last year. Nice park in a quiet location.

Do a Google search for `______ tourism' and put the State, City or area in the blank and read what the experts have to say. I always recommend Mill Creek CG in Mackinaw City with a visit to the Island.
And you have to try the Pasties in MC a local historic staple. See how the Bridge was built at a free film upstairs from Momma Mia's pizza restaurant.

This may help ya.
http://www.michigandnr.com/parksandtrails/ParkMap.aspx

Can't help with RV parks but I do know a few of the sights!

Sleeping Bear Dunes National Shoreline
Lots of lighthouses
Pictured Rocks National Shoreline
Tahquamenon Falls
Big Springs (Kitchitikipi)
Hartwick Pines
Mackinaw City/Mackinac Island
Soo Locks

Are you traveling with children? If not, there are great wineries in the Traverse City/Old Mission and Leelanau Peninsula areas. Wine (and brewery) tours are popular.

check out Indiana Dunes State Park.

Any route going north along Lake Michigan heading toward the Upper Penninsula. Stay away from Detroit and eastern part of the state !!!