Check out the 2 COE Campgrounds, Cage Bend & Cedar Creek. Both are right on Old Hickory Lake and very nice. We were the Hosts at Cages Bend for the past 2 summers. They are both about a 1/2 hour drive to Nashville.
Otherwise, if you want to be closer into Nashville then check out Two Rivers RV Park (Older park & spaces can be a little tight), Nashville KOA (Very nice park and has recently gone through a major remodel) and Yogi Bear Jellystone Park. All 3 are right next to each other on the North side of Nashville. There is a Camping World right between them and another RV Dealer who is also a Montana Dealer. They are located about 1/2 mile from the Grand Old Opry and the Opryland Mall.
PM me if you have any questions.