That's hard to say... Last week it was 82 deg high and 51 low. Today high 65 low 56.
Aug-Sept is usually pretty warm. I would say September is better than Aug though. Our "hot" is not a normal hot. Its a very humid hot...sorta like walking in the steam above a pot of boiling water.
There is one go-cart place but its not very good. Maybe instead of go-carting we could tour the Jack Daniels distillery http://www.jackdaniels.com/visit its about 1 1/2 hours away.
The other thing to mention is Knob Creek, KY. It would be 2 1/2 hours away but its something I've always wanted to do. October 14, 15 & 16, 2016 is their machine gun shoot dates for next year. If you aren't familiar with it, just watch this http://www.knobcreekrange.com/media/video
Neither of those are in Nashville itself, so we would probably only be able to do one of them.