I make that trip every November, and the return trip every spring. You have some long drive-days ahead of you! I prefer to stay in state park campgrounds. Over the years, I've found some beautiful campgrounds at prices that are significantly lower than hotels/motels. Once you get south of Indianapolis, you'll find most state parks open this time of year - although the water will be shut off (until you get into Oklahoma). Every year I find more and more state parks are requiring
reservations, so plan accordingly. There's a really nice state park about 15 miles east of Norman OK called Lake Thunderbird, where I stay for a couple of days every year.
Campgrounds are hard to find around Dallas. I've found only 3. Stay away from Sandy Creek! It's a mobile home park that allows RV camping. The sites are very small, and the residents let their dogs poop anywhere and everywhere. And they don't pick it up!!! I always spend a few days at Hidden Cove Marina & Campground in Frisco (on the north shore of Lake Lewisville). It's a little pricey but has large sites with full hook-ups, and the staff is very friendly! Just stay off the freeways/tollways between 6:30-9:00 am, and 4:00 to 6:30 pm!
I spend the winter near San Antonio, which (at 65mph) is about 7-8 hours from the north side of Dallas. Houston will be about 10-12 hours. I haven't been down to Houston, so can't offer any camping suggestions there. Just remember to enjoy the journey as well as the destination!