Lots of great roads mentioned, so I won't repeat. But don't forget a UP food staple: the pastie! When you get to the UP take US2 west and stop at any of the little roadside shack restaurants for some of the best anywhere.

 

Since you are that far Pictured Rocks is a must stop, also on the way up Bear Dunes area is scenic...

 

Thanks for all the suggestions. Plans are coming together. It looks like there is enough to do in the U.P. to make it a trip of it's own.