New Mexico & Texas trip suggestions please

We're planning a trip to New Mexico from Toronto. We'll likely leave the end of April 2017. We'll travel to New Mexico through Missouri, Oklahoma & Texas. We're looking for suggestions of "must see" along the way. Most of our time will be spent in Texas and New Mexico. We'll likely travel through Colorado on our way home.
Any suggestions of campgrounds and places to visit would be appreciated.

April would be an ideal time to visit the Texas Hill Country, and also East Texas. But I have a feeling that "through Oklahoma & Texas" means to a lot of people to take I-40 from Oklahoma City to Amarillo. If that's what your route means, I hope you will consider a change to include East Texas and the Hill Country. Places like Caddo Lake, Tyler State Park, then down to Fredericksburg and Kerrville

The only thing is that this is still a long way from New Mexico. Northern New Mexico and Colorado are two of our favorite places, especially Santa Fe and Taos (and the High Road between them). We were just at Santa Fe in September. We always stay at Santa Fe Skies RV Park.

This could go on and on, but I'll just stop here.