Hello,
I only fish streams, so I cannot provide much regarding lakes... Trout inland fishing seasons usually end at the end of September. Please, keep that in mind.
I believe you will not see any stream trout action until you hit Duluth in MN right before entering Wisconsin. I would suggest buying your fishing licenses online and getting the regulations ahead of time. They have some great maps. In addition, the Department of Natural Resources (DNR) does a great job in providing online information and maps. Here are some useful links.
Minnesota: MN DNR
Wisconsin: Wisconsin Maps by County
Michigan: Michigan Trout Overview
I have not fished up north for a number of years (I live in Minneapolis), but there are some great midwestern streams in Wisconsin and the Upper Penninsula Michigan. That is going to be a heck of a trip. If you want trout, I would not spend any time anywhere until you hit Duluth.
Highly recommended that you get this book. It was quite controversial a few years back due to the "kiss and tell nature":
Trout Streams of Wisconsin and Minnesota
For Michigan, I cannot vouch completely for these two, but probably well worth getting, especially since you will cover so much of Michigan:
Flyfishers Guide to Michigan
Trout Streams of Michigan: A Fly-Angler's Guide
Spending $60 in books might be well worth it. There are a lot of streams.
Shoot me a PM once you have iron out your dates / trip and I will try to give you a few more tips. There is a fly shop in Superior (WI) and another one by the Brule River (WI) that might be beneficial to hit. Upper Peninsula is not that developed, so it is difficult to find good shops / info...
Good luck
Alex