Probably only about 30 minutes to Chattanooga. Rock City and Ruby Falls are also worth seeing there.
You might check out the route to Fields of the Woods in North Carolina. It's an interesting display of some biblical things that your church camp kids might enjoy.
Not real close, but an interesting area is Tellico Plains and Bald River Falls.
Just up I-75 a few miles is Sweetwater, where Lost Sea is located. All my kids went there on school field trips and enjoyed it.
The Ocoee River was the site of some of the olympic games in 1996. It's an interesting drive along the river (though closed right now because of a major rock slide). Depending on how much time you've got, you can keep going toward North Carolina and hit some of the interesting North Georgia towns like Young Harris.
Sheila