If you go to the Soo, the restaurant right across from the locks serves some of the best whitefish I have eaten. We always plan on eating there when in town. there is an old freighter that you can tour in the Soo as well. One of the coolest stops I've done. Walk the ship top to bottom.
x2 on the shipwreck museum as well.
If you make it that far, check out
http://www.oswaldsbearranch.com/. Ten dollars a car load. See the bears up close. This is a local man who moved to the U.P. and takes in orphaned cubs from all over the country. It's not far from the museum and Tahquamenon Falls.