Considering you'll be hauling delinquent teens, I'll add a couple comments. The Sleeping Bear Dunes will give them a look at sand and dunes that is quite different than the Gulf shores. Depending on the weather, they can take a dip in Lake Michigan but its likely to be a bit cooler than Gulf water temps. Of course it's fresh water. I don't remember when you'll be going through the area but this area is loaded with cherries and other fruit during the summer.
Mackinac Island is a great historic site. The are no cars on the island so you'll have to walk, rent bikes or take a horse drawn carraige. Whether you take carraige or not, your scoundrels will likely remember the smell of horses for years to come (if you know what I mean).
In the upper peninsula of Michigan, tahquamenon falls is a nice stop and not too far off I-75. There are two sets of falls (one small and one pretty tall) and a nice state park. When you get to Sault St. Marie, MI, I recommend a burger at Clyde's Drive-in. It's on the channel that seperates Lake Superior and Lake Huron so you are likely so see some of the big cargo ships going through the locks and the burgers can't be beat. There is a boat tour that you can take through the locks but it might be a bit boring for mid to late teens.
Once you get to Ohio, I'll add a ++ to Cedar Point. If your delinquents are tired of being hauled to boring places, all will be forgiven after a day at Cedar Point. Just be forewarned its not a cheap place to take a family. Check online to see how you might get discount tickets.
Enjoy your trip. You'll like the pleasant summer weather.