In TN we first stayed at Pigeon Forge KOA, great place right close to Dollywood. We had a blast here at Dollywood and the local amusements leading into and around the park, you have to see it to believe it. Mooshine is also legal and free to sample on the blvd in Gatlinburg, walk around and enjoy all three brewers. There are rocking chairs and plenty of folks dancing, have a good time as it's a bit different way of life. Take a drive through the smoky mountains if time permits.
Nashville Country RV park, great place as we stayed here without reservations during the country music festival (we didn't know it was going on that weekend) last summer. These folks made us welcome for 5 or 6 days. Went to the Grand Ole Opry but didn't tour, just visited the old site as there was plenty to see during the CMA fest downtown. Amazing what some of the musicians went through during the days of Johnny cash etc. No matter what bar you stop in at there is no such thing as a bad house band! Everyone is trying too be the next big discovery and they all work for tips.
Johnny Cash museum, well worth it. The Hermitage mansion, it was ok, DW loved it.
In Memphis, Tom Sawyer rv park (just across border in Memphis AR, not Memphis TN, about 25 mins from Graceland) has some great hosts and all very friendly, real cool barge traffic on the river right in front of your site. Graceland, what can I say except you have to do it. We did the normal tour seeing the mansion and the planes (can't remember if that was platinum or not) but a good tour. Stop in and get some of the best shake & baked catfish down the street while you are around this area. Do the Sun records tour, Stax museum of soul music and the rock & soul museum, we had a blast at all 3. You have to go to Beale street if you like music. Go the first time during the day to feel more comfortable, after dark the panhandlers come out. We felt very safe but some might not after dark. I would also recommend going to the Martin Luther King civil rights museum. So much history here its hard to believe. Most of us are old enough to remember that day on the evening news at the Lorraine motel but it's surreal to see the exact balcony and rooms etc. all preserved.
We spent 7 days in Knoxville around Dollywood area, then 6 days in Nashville area, then another 6 days in Memphis area and all 3 places had us going to visit something specific every day, take as much time as you can and google everything to get an idea of some kind of schedule. Try for reservations on Friday or Saturday otherwise you will probably be ok. Hope this helps.