Stop in Schulenburg, and take the Painted Church Tour, it's several hours of driving and looking, you can stay at Schulenburg RV Park, nice, clean but not fancey. Then travel on through San Antonio on IH 10 to Boerne. Stay at the Alamo Fiesta RV Park, very nice, friendly folks, easy on and off freeway. Then you are about 30-45 minutes from anything in San Antonio, The Alamo, River wailk. Park in garage or lot and take the painted buses (trolleys) and go all over San Antonio, on and off all day for 1 small fee...$1 or $2.. really worth it as the drivers tell you what is nearby or what your passing. Also from Alamo Fiesta your 15 min from Water World and 45-60 min from the "Hill Country",, Comfort, Kerrville, and Fredericksburg. And Boerne has good food and shopping also. I would plan on spending 3 days in SA area at least.
Try to spend a half-day at Enchanted Rock State Natural Area just north of Fredricksburg. One of the more interesting parks in the area, and you'll see why when you get close. Unfortunately there are no RV sites there, but there are places in the general area to overnight an RV.
We are in the beginning stages of planning our summer trips for 2012 and I am excited! We are still trying to decide on a trip through Texas or up through Arkansas and to Branson. We have been through each state and places, but never with a camper (we just bought our camper last year and only went to local spots close to us).
We were thinking if we do Texas routes to head back to San Antonio, Fredricksburg and other places that way. It is my goal to find all the hidden gems and special places to visit that we normally would not get to see when we make just weekend trips to these locations.