I've done quite a bit of camping in the UP of Michigan and have been really impressed by how much beauty can be found up there. Doing Pictured Rocks, Tahquamenon Falls, and Kitch-iti-kipi on a 4 day weekend trip is pretty incredible. So I'd do Isle Royale and hot up a few more landmarks while being up there. Sounds like a good clean inexpensive trip!
As a Michigander Hocking Hills literally changed my view on Ohio. Incredible place. We did an early spring trip with a cabin and hot tub. We want to go back in the summer during better hiking conditions.