Gail and Steve,
We just completed a similar route from Southern CA to Memphis.
We stopped in Tucson (visiting relatives) and stayed at the Lazydays KOA (huge and full). The Biosphere II is a really neat thing to see. I'm sure you have seen it if that's your home-base.
Next stop, Las Cruces, NM at the Hacienda RV Park (one of our favorites). The Double Eagle restaurant in the 'Old Town' not far away is excellent! It's in a 150 yr. old Adobe home on the Square. If you like Banana's Foster, I highly recommend it!
We don't care to drive through Texas if we don't have to (long and boring scenery). If you go to San Antonio, the Alamo is a must see and the Riverwalk shopping area.
This trip, we drove up the I-25 to Albuquerque staying at the American RV park. They have a new section just for large RV's with toads.
Next stop, Tucumcari, NM, at the KOA (muddy when wet and it was wet, LOL). They have a good Dinosaur museum on the main road in Tucumcari.
Next stop, Amarillo, TX. We always stay at the Big Texan RV Ranch as it's close to the Big Texan Steakhouse where you can eat the 72 oz. steak and all the fix'ns for Free if you finish it, otherwise, it's $72.
You can schedule a free limo ride to the restaurant. You don't have to stay at their park to use the service, they will pick you up/drop off at just about any of the nearby parks/hotels. Most of the time, you will see people trying the Big Steak. While we were there, two people were attempting it, I don't think they made it as we left before they finished. They give you an hour to eat it all! The food there is good.
The Jack Sisemore Traveland museum is in Amarillo and is neat to see. They have the RV that was in the movie with Robin Williams (the old red Flxible Starliner) and many antique RV's of all kinds.
Next stop, Oklahoma City at the Mustang Run RV Park. This is a very clean park with all concrete sites and road. The American Quarter Horse Museum is there and I hear that it's a must see. We'll do that one day ourselves! The original Capitol was in Gutherie, OK, just north of Oklahoma City. Nice little town to seek out, we enjoyed touring it.
Next stop, Russellville, AR, at Ivy's Cove Resort (a nice small family owned RV park). It makes for a good stop before driving into Memphis.
Are you going to see Graceland while in Memphis?
Safe travels and good luck!