You've gotten some great suggestions above and I agree with them.
One not mentioned, and this was a high point for our trip, is to drive up the Keweenah Peninsula (NW part of the UP) to Copper Harbor, then head over to Fort Wilkins. We enjoyed camping there quite a bit. Easy walk to the Fort where they have living history staff - you step right back into the days of the fur trading, boys going off to the Civil War, etc. We found it fascinating!
On the way back, drive through Mandan. It is a ghost town with great cell phone reception (go figure).