I can't even begin to suggest campgrounds as we so seldom use them, and without knowing what you would be interested in seeing (like museums, scenery or history) I can't even be much help other than the suggestions you do have above. There are AAA guide books and the state's own tourist information, but there is just too much to see in the area you have outlined. Last year we spent a week between Chicago and Escanaba just picking up the things we had missed or wanted to see again.
Matt