Visit Mackinac Island while you're up there. Stay in Mackinaw City and take the ferry over for a day of biking, tours, shopping, etc on the island. We actually stayed on the island for a week a few years ago. If you like, catch a fishing trip on Huron for lake trout and such out of St. Ignace or Mackinaw City. Good time.
We didn't spend a ton of time on the UP, but St Ignace is a cool little town. We took Hwy2 west along the south side of the UP and went to Brevort. We had friends with a cabin over there. There's a couple places on the north and south side with huge sand dunes and beaches that are pretty cool. You can also go up to the Soo Locks in Sault Ste Marie and watch the huge iron ore ships go through. I've seen them in Duluth and they're pretty darn cool.
There's a bunch of state parks and national forests and such on the UP and random towns. You could ferry out to Isle Royale National Park on Superior. Cool areas to kayak/canoe. Fishing. Etc. Idk when the leaves turn up there but historically "the skies of November turn gloomy." I wouldn't want to be up there much past September unless I was hunting lol