Love Muskallonge Lake State Park. Very pretty with lots of lake view sites. You can cross the street to Lake Superior and look for agates. Nice to visit both Pictured Rocks and Tahquamenon Falls.
There's a nice camp store near there (Deer Park). I believe they also rent boats. Nice fishing lake near there, too, called Perch Lake.
And if you go into the great metropolis of Newberry, check out the ribs at Timber Charlie's.
I haven't camped there, but Marquette is an awesome UP town. Check out the UP museum. Lots todo (it's a college town).
Hope you have an awesome trip in my adopted state.
Try michigan.org for other ideas.
Owners of a 2013 Sunseeker 3170 Class C beauty. We travel with two shih tzu, a leonberger and, oh, yeah, two teens and a 6-year-old.