@silly123 If you have younger kids Splashtown would be just fine. They have all sorts of slides and a lazy river. It is alot bigger thant it looks from the freeway. Plus it take less time to get there than Galveston or New Braunfels (3 drive for a waterpark?, not me).
Shlitterbaun in Galveston is nice, but when we went we mixed it in with a stay at Moody gardens, that was a good weekend. IF not for the stay, I wouldnt make a trip just for the waterpark. The lasy river is better than spash towns, other than that I see no difference.
Regardless which waterpark you go to get there once they open to beat the crowds. IF you go to spashtown pack a cooler for lunch. You can't bring it insid, but it's notfar to get pack to the lot eat.