You have a couple of options right off of I 10 One is Stephen F Austin State Park Park Rd 38, San Felipe, TX 77473 about 30 miles outside of Houston
Another is West Houston campground which is just outside of Katy Texas just west of Houston
http://www.hwrvpark.com
There are many ways to get to corpus outside of Houston. One route 59 S. Or you can take I 10 west and pick up some routes off of I 10 heading south just remember Houston traffic is really bad heading west in the afternoon starts up about 3 o'clock and can continue as late as 7 PM
Irish Tinkers