If you have an extra day, and enjoy roller coasters, I would highly recommend Cedar Point in Sandusky Ohio. Widely regarded as the best theme park in the country, and certainly the best I’ve been to.
Been to southern Michigan/northern Ohio too many times to count as my dad grew up there and still has family there. Unless you like to hunt, Michigan doesn’t offer a whole lot. If I didn’t still have family there, I would probably pass on the trip.