Columbus is a neat little town. There are usually good shows going on there during the summer; if you have time see if there are any concerts happening!
If you guys magically have any time away from the convention center and aren't drowning your sore feet in epsom salts and/or beer, there are a lot of lovely places around town to visit. For instance, Dublin's concrete corn field, German Village, Schmidt's Restaurant, The Book Loft, the North Market, Short North, Easton Town Centre, etc. Also, both Gallery Hop (in Short North) and the Columbus Arts Festival (downtown) are this weekend, and a lot of fun. Too bad it's so hot.
I'd be happy to traipse around town if you need a guide, or at least provide directions to some of the necessary sights to see (Schmidt's is definitely necessary - good beer, lots of wursts, legendary cream puffs, and a live tuba/accordian band on Saturday nights). Just email me at krysta[dot]galehouse[at]gmail[dot]com if you want more info!