Call directly: Brazos Bend SP, Huntsville SP, Galveston Island SP, Buescher/Bastrop SP's. Cagle Recreation area is by Lake Conroe.
Crockett Family Resort is not too far. I've camped at the all with my Pup.
Oh, I forgot Spring Creek Park in Tomball. It's free w/full hookups! Go to:
Precinct 4 Parks