Uh... Ohio may be "the heart of it all" but with so much closing around here, unless you're doing the tourist thing there isn't much to do! Except FESTIVALS. And most of those are in the fall.
Around Dayton area... AF Museum, Boonshoft, Art Museum, Union Station (that's Cinci). I think there's a planetarium but it's been years. COSI (in Columbus), kids museum (Indianapolis). There's a SWEET B&B/spa about an hour north of Dayton - went in March with my Mom - husband and Dad got together and gave us a weekend there for Valentine's Day.
Lots of river to canoe on... Some woods to camp in... Shopping of course and a slew of universities. Otherwise... YAWN... But then I live here. on the other hand, there are a lot of good family restaurants and the cost of living isn't so bad. Plus I have a good job!