I've lived in the Memphis area for 66 years, and these post are some good info.
I would stay at the Graceland RV park for convenience, and take the shuttle to Beale St., and Sun Studios. My dad George Pierce was the photographer for the Million Dollar Quartet photo btw. I grew up a few blocks from Graceland, but sadly now its a little risky to shop or eat in the area.
Then head to Nashville to see Broadway,The Country music hall of fame, the Hermitage just to name a few, and on towards Severeville, and Gatlinburg.
You are welcome to PM me any questions.