Texas is not my favorite place but San Antonio's River Walk is really nice, and the Alamo is worth the time too. Further North is Canyon, 13 miles south of Amarillo, it is a neat little college town with a great Oil Field Museum. On the east side of Canyon is Palo Duro Canyon. It is not well publicized but a nice overnight stop, nice campgrounds down on the canyon floor. Not sure about the weather at that time of year but it does get very cold there. In Amarillo is Jack Siezmore's RV Land. He and his son have a great museum out back. Well worth the stop.
My next stop would be Carlsbad, I waited 60 years to see the Caverns, saw a film strip or two in grammer school and always wanted to go there. The DW had no interest but in May of '14 we stopped there going east. About 100 feet into the main room she was amazed and wants to make sure I get back in the summer to see the bats.
From there to the Canyon via I40 to Williams and then to Trailer Park if you want/need hookups, Mather for dry camping. There are some great sites there and a myriad of things to do and see. Check out the Ranger programs, go to Kolb Studio, Hermits Rest for sunset, Bright Angel lodge for ice cream, See the fireplace in the lodge with rocks that Mary Colter hand picked from each strata from the river to the rime. Do the Walk of Ages and take lots of photos.
Back down to Williams and the west and up to the Dam. Check the night before to see if they are giving tours. With the attack in Paris, security will still be very high and the dam may be closed.
I could go on but I'd need to know how long you'll be there.
Also if el nino is really bad, there may be some rain although the monsoons are over until next spring but Zion may well have a lot of trails closed due to high water in the slot canyons.
Have fun and try to come back, we'll give you an itinerary for at least three months of sight seeing.
