Our favorite is Muskallonge Lake State Park. Just electric at the sites. Many have a lake view even if not right on the water. They can accommodate big rigs. You can do day trips to tahquamenon falls and pictured rocks. There's a great store down the road, Deer Park, where you can get anything you need and rent a boat: http://deerparklodge.typepad.com/deerparklodge/2007/04/muskallonge_lak.html
You're also across the street from Lake Superior. Pack a picnic lunch, hang out and look for agates. Perfect!
Have a safe trip.