Certainly consider touring Ohio State, one of the largest university campuses in the U.S. Ohio State has superb athletic facilities and perhaps you could arrange a tour given the size of your group. Golfers in your group likely would enjoy the Jack Nicklaus Museum there.
A visit to the mammoth Ohio Union (student union) and Thompson Library wouldn't require an organized tour of the OSU campus.
North Market might interest your group. It features the original Jeni's, which offers some of the best and most original ice cream in the U.S. Graeter's also is among the best ice cream in the U.S. and actually offers a factory tour in Columbus.
You could tour the Ohio Statehouse and the Ohio Judicial Center is an Art Deco gem and has a very good, interactive legal museum oriented toward pre-teens. You should pre-schedule tours for both venues given the size of your group, but it's not necessary for the Ohio Statehouse.
Check out the Ohio Historical Center and the Ohio Exposition Center to see if events at either would interest your group.