What kinds of things do you like? A quick detour to Dearborn, which is on the far west of Detroit, will get you to the Henry Ford Museum, which is indoors and has tons of things Henry collected, including cars, industrial machinery, the car Kennedy was shot in, the back-of-the-bus bus, and his old camper-kitchen, plus some trains and thousands of other things. Worth several hours. Next door is Greenfield Village, which is an outdoor museum with historical buildings Ford bought and moved to the facility. Also worth several hours.
And from the Ford Museum you can get tickets for a tour of a very modern assembly plant. They will take you by buses and explain the assembly processes as you walk on a long catwalk.
Near Grayling, MI, is Hartwick Pines SP, which has a logging museum and a stand of virgin white pines to walk among. Campground has some full hookup sites and is nice.
And of course, you will want to spend a couple of nights near Mackinaw City, MI, and take the ferry to Mackinac Island to see a Victorian island that does not allow cars. You take a horse-drawn carriage tour or rent a horse drawn carriage or just ride your bike 8 miles around the island on the only Michigan State Highway that does not allow motor vehicles!! Visit the fort and buy some fudge while there. (Good parking in Mackinaw City, one block south of the main street or under the Big Mac Bridge, but be very careful of the one street that goes under the bridge with low clearance. If you take the ferry to the island, ask about where to park, and they will direct you to RV parking.)
Another detour north of the Big Mac Bridge will take you to Sault Saint Marie, MI, where you can watch the big freighters go through the locks. They are close enough that you can wave at the workers on deck! A basic campground a mile east of the locks, but with close views of the ships, is Aune Osborn Campground, which is owned by the city. There are electric hookups on dirt lots, but this is a case of location, location, location!! There is also a lake freighter nearby you can tour.
Heading west is Taquamanon Falls and Whitefish Point where you can tour the shipwreck museum and artifacts from the Edmund Fitzgerald, a 1000' frieghter that broke in half during a Lake Superior storm and was the subject of a Gordon Lightfoot song.
Also, you will enjoy the drive along either the Lake Superior or Lake Michigan coast.