re: Michigan resort towns

If you're willing to extend the drive to around 4 hours, there's much better options... Traverse City, Torch Lake, Sleeping Bear Dunes. My wife (no pics) and I live in the Detroit metro area and love that area. Depending where in Detroit you are, it's roughly 4 hours (takes us under 3.5 from Royal Oak to Traverse City).

There's some good areas on the west side of the state that take 3 hours to get to. I have friends that spend a lot of time in Muskegon, South Haven, and New Buffalo. I haven't been, but they are Michiganders and love it.

Lexington is another small coastal town less than 2 hours from Detroit that I get recommendations for all the time. I feel like you can't really go wrong with most towns on either coast as you move north from Detroit.

Someone mentioned Put-in-Bay in Ohio... if you're looking to do some heavy drinking, that could be an option. I've only been for a couple group outings where that was the goal. I'm sure it will be very busy at any point in August, but then again so will most nice places along the Great Lakes.