I hate to promote Dinosaur Valley SP because I think it already gets more hype than it deserves, but my 3 yr old and I had some good hikes & camps there. The campground sites are hard to get and the backcountry sites are awful, but there are other places in the area to camp.
Cleburne SP would be good.
Lake Benbrook has some nice Corps of Engineers campgrounds:
http://www.swf-wc.usace.army.mil/benbrook/main.htm
Lake Ray Roberts also has some great parks:
http://www.swf-wc.usace.army.mil/lew...RayRoberts.htm