2 summers ago I started out in MN but after a few days it got into the mid 80s along the shore, so I drove to the UP. I spent a night at Porcupine Mtn SP and 3 nights at McLain SP, and it was mostly upper 70s but did reach 82 one day.
I think the breeze moving easterly off the lake makes the Keweenaw Peninsula state parks a bit cooler, although it's not a big difference. This year, with the ice in the lake, I'd expect the lake effect along the shore to be more pronounced than usual.
Both the MN shoreline and the UP shoreline are picturesque. Why not spend some time at each?
If you have trouble getting into the state parks (weekends could be especially tough), try the forest CGs or municipal CGs. For example, Tettegouche in MN may be full, but Eckbeck state forest CG just a couple miles up the road toward Finland should have room. McLain in MI is wonderful but if you can't score a spot there, try Ft Wilkins farther north, or Gratiot River County Park not far north of McLain, or one of the CGs in Houghton/Hancock.
As for eating out, I have only one recommendation: a pizza at Sven and Ole's in Grand Marais. (I don't eat out often when camping.)