+1 for the UP. A must see. Also, for the Lower Peninsula, riding along the western side of the state is generally better than the east. Less populated and more interesting terrain. Plus lake Michigan is pretty amazing once you get up near Empire (a bit west of Traverse City). If you make it out that way, check out the sleeping bear dunes!

I would take the time to explore northern MI; its really pretty country once you get out of the industrial areas. Tons of rivers, inland lakes, forests, and of course the great lakes. I'd suggest going north rather than heading south from Lansing. IMO northern OH and IN are pretty uninteresting.