From Cinci you are looking at a good 10-12 hr. drive to Chattanooga, then another 12 hr. day to Orlando so if you are wanting to see attractions in the area then an 2 night stay is required. I also think Chatt is the better choice for things to see and do over Atlanta for the kids. Aquarium is one of the best even though ATL has a very nice one as well. The Incline Railway/Lookout Mountain is pretty neat too.
Rock City and Ruby falls are interesting and there is the Creative Discovery Museum with hands on exihibits for the kids. Lots to do.
