We visited the UP about 6-7 years ago... some of those highlights were...
Soo Locks at Sault St Marie
Whitefish Point Lighthouse and G Lakes Museum
Pictured Rocks Nat Lakeshore near Munising
Twelvemile Beach campground... primitive no hookups and no reservations, but stop for the beach anyway... crystal clear cold water and nice sand from the sandstone around you. There are 3 other National Park campgrounds in that area, all with no hookups next to the lake.
St Ignace state campground with bridge overlook from campground
Macinac Island day tour by ferry boat
If returning thru OHIO, then
Get the guided tour especially if you grew up with Motown music in your youth...