Sounds like a good trip. On my recent road trip I stopped at as many chargers on the way out as possible. Then on the way back, I had a lot more knowledge about what was nearby, which ones were easy to access and so forth. It made the return go pretty fast.
I would expect that west of San Antonio you'd have to stick closely to Interstate 10 as much as possible and not pass by a Supercharger. I'd also plan to bring the 120 charger, the 14-50 pigtail, the charger adaptor for ChargePoint and be ready for the unexpected.
If you can find a hotel with charging in the Big Bend area, that would be worth the extra dollar or two.
Enjoy and I look forward to reading the trip report. As a Texas native, I've still never been to Big Bend and it is on the list.