Fate Sanders rents boats and Elm Hill Marina rents boats too. If your folks like next to the dam, Elm Hill may be a little closer to you. They make you park at the top of the hill and pay a parking fee there though (and the hill's steep). Keep in mind, if you're fishing on the dam side of the lake, which Elm Hill is, you'll be fishing in slightly cooler, deeper water. There are some good coves and islands along the channel right out of the Elm Hill.
If you go for the bank fishing at Old Hickory Lake, there is some good shoreline with rock, brush, and fallen trees in the Shutes Branch ramp cove off of Saundersville Road. It may be a little shallow for crappie though due to our recent cold front. I haven't been out there in a couple weeks so I'm not sure how deep they're holding at Old Hickory.
Good luck out there, and welcome to Nashville.
Mistah Kurtz - he dead
A penny for the Old Guy