We worked our way across the UP on our way back to Upstate NY.
In no particular order:
Of course Mackinac island. We rented bikes as they said e-bikes are not allowed. We did see people with them on the ferry and they did't get turned away.
Straits State Park has good camping. Very close to the island ferry terminal.
The museum at Whitefish Point is well worth the trip. They have the recovered Edmund Fitzgerald bell.
We stayed at Tahquamenon Falls State Park and went to the museum from there.
Bay Furnace campground was fantastic. Really helpful hosts.
Miners Castle is worth the trip.
One final note. Michigan Park Pass.
https://www.michigan.gov/dnr/buy-and-apply/rec-pp