We were there on Tue Wed and Thur of last week. Used the Terraport, visited Wapak, the old canal at Piqua & New Bremen (plus the bike museum there), Indian Lake, Piatt Castles, etc, etc. Took the kids to the Elder theater in downtown Jackson Center ($3 for the show), and the swimming pool in town too. Kids (4 & 8) had a great time. We all got shirts :-)
Over this past weekend, we dry camped at Kiser Lake State Park - great activities for the kids. The naturalist & volunteers really put out a lot of effort.
Indian Lake has a State Park too, but it was full. the beach wasn't bad though.