Recommedations

Natchez ,Mississippi . Free three day stay at visitor center with water,elec.and dump ! The price is right , I wonder if ya can get a senior discount ?

Thank you all, I will write all these suggestions down.

Caverns of Sonora near I-10 close to the town of Sonora. It is on a private ranch and has a small RV park. It is nothing fancy, but handy for seeing the caverns. They contain some pretty spectacular formations.

I would recommend Balmorhea State Park off I-10 in West Texas, but it is closed until Spring 2020 for renovation. It is the world's largest artesian spring fed swimming pool & open year round. Maybe on a later trip?

Also a short stop at the Texas Canyon Rest Area on I-10 near Willcox, AZ is worthwhile. You may already know about this. When we stopped there a couple of years ago, some folks in a small Class A were so excited about getting out and checking out the view that they forgot to set the parking brake in the rig. It rolled down the entrance ramp back to the highway and crashed into the ditch. They were being pulled out by a big wrecker and had a smashed windshield at a minimum.

You didn’t say where in FL you’re starting, but the Naval Air Museum in Pensacola, Gulf Shores, AL, New Orleans, Texas was mentioned but I’d add the Tx Hill Country, Carlsbad Caverns in NM, Bisbee, Az mine, Tombstone, AZ, Kitt Peak observatory outside Tucson, as well as Old Tucson western town.

Certainly the Space Center in Houston. On the assumption you are just making an I-10 run there will also be a whole lot of nothing!
Pensacola and the Destin area are spectacular.
New Orleans.
The Alamo
Kerrville, TX - Buckhorn RV resort if that stop works with your travels.
El Paso (NOT! Great place to bypass)
White Sands would not be much of a detour.
The Very Large (Antenna) Array in Socorro, NM is interesting if you like learning and you happen upon the right weekend.

Get off the Interstate Highways and travel the side roads whenever possible.
I like to use Roadside America when traveling. Maybe you can find something interesting along your route.

Big Bend National Park, if you haven't already. Wouldn't do Palo Duro after Thanksgiving, in fact you want to stay I-10 or south of it.

Coast Bend area (Corpus Christi), Goose Island State Park in Rockport. From there, get on US 50 and head west to Marathon, then dip south to Big Bend.

Alamo in San Antonio TX for a historical stop and you will be surprised when you get a look at the place.

Palo Duro State Park south of Amarillo TX. Stay a couple nights and watch the dinner theater. This is on the I20 route.

Not a lot along I10 in TX, FT Stockton has an old cavalry fort that worth a couple hours.

New Mexico is loaded with National Parks along whichever interstate you take. On the I20 route there are a number of Indian Pueblos you can visit, the Taos Pueblo is quite interesting

Along I10 is Carlsbad Caverns an absolute must stop, it is the most spectacular cave in the National system.
Also White Sands is worth a few hours, it's best seen in the early morning or around sunset.
Gila Cliff Dwelling is something of a diversion north of the Interstate north west of Deming. Near Silver City is the City of Rocks State Park worth an over night stop.

We don't know where you are going in AZ so it's hard to make suggestions. Like NM it is loaded with interesting stops.

I found the Vicksberg National Military Park interesting. Visited twice over the years. Each state seems to have built a marble structure honoring their soldiers. Illinois’ was the largest as I recall.