You are just over 2 hours from Cedar Point, which is one of the top amusement parks in the world. And you are probably not much further to Six Flags Great America north of Chicago.
On Lake Shafer in Indiana, you have Indiana Beach and further south is Holiday World with some great rollercoasters and waterpark.
There is also Six Flags in St Louis, Kings Island in Cincinnati and Kentucky Kingdom in Louisville.
If you wanted to venture out further, there's Adventureland in Des Moines and Worlds of Fun in Kansas City, Kennywood in Pittsburgh, Canada's Wonderland north of Toronto, Waldameer in Erie and Hershey in middle Pennsylvania.