Wow, I'm familiar with the area, but not familiar with any RV parks in those areas.
Here is how I would approach it. I'd go to RV PARK REVIEWS and see what is being reported on in the reviews. I'd go to the web site of any parks I had an interest in and see what they say about their own park. (All good I'd expect.) I would then use one of the on map services and get a birds eye view of the park to see what the spacing is, and the general lay out.
www.bing.com/maps provides birds eye views of many areas. Then, call the chamber of commerce and see what they have to say. Also, you could call the local police department and get their take on crimes in the area.
I wish I could be of more help. If you get a little closer to the Galveston area, I could recommend a few CG's.
Good luck.