The Thumb of MI and Bay City are both nice places to visit. It all depends on what you are looking for.
But in this case, TC is the place the OP wants. LOTS of things to do, fantastic scenery, etc. We enjoy Bay City (no kidding..lol) for shopping for antiques, dining out, watching the river traffic from a couple of restaurants with decks. We like some of the history there we like to look into. The Thumb is quieter, has some very small towns, some nice campgrounds, hiking, fishing, boating, farms/farmstands etc. but I don't think that is what the OP is looking for -we all felt TC is the place for them this trip.
Edited: 9:32 am, August 07, 2011