Mike,
On the UP, have a look at going up to Copper Country; the Keweenaw Peninsula north of Houghton-Hancock. There's a bit of lakeside driving on mill talings dump "beaches", some high ridge driving with great views of the water, a deep mine tour of a native copper mine, and several quaint towns and villages. On the way there, north-northwest of Marquette, you can do a drive-through of the Huron Mountains, which includes Michigan's state high point. There's an old railroad grade (Peshekee Truck Trail) which connects to some FS and county roads on the Skanee side. Point Abbaye is a drive-to within 25 yards of the lake, with views of the Huron Islands, Huron Mountains, and the long ridgeline of the Keweenaw Peninsula. Be sure to snag some pasties to eat from the little pasty shop on US 41 in Hancock and a huge and yummy cinnamon roll at the shop in L'Anse.
For general planning, check the schedule for the Lake Superior Rally, the successor of the old SCCA "Press On Regardless" which is still run in mid-October. Houghton-Hancock will be fairly booked up with rally teams and spectators that weekend. On the trip out or back, be aware of the possibility of difficulty in finding motel rooms in eastern MT (generally along I-94 east of Billings) and most of western ND. The Bakken Shale oil patch is likely hurting due to the dramatic drop in oil prices, but as recently as a few months ago it was still pretty tight in terms of finding a place to stay overnight.
If you go through the Nebraska Sandhills, take a half-day to arrange a tanking trip on the Middle Loup River right outside of Mullen, NE. Tanking is a great way to see part of the Sandhills seen by only a few.
Foy