The river is the place to be
This is smaller state park but it has everything you need. Larger sites, lots of shade and a cool river to swim in. There aren’t much in the way of hiking trails but to soothe your ills just walk down to the Blanco river and hang out in a tube or just swim. The sites all have a covered table which is really nice during the summer. There is a rock walled area that is the “kiddie pool” area that is really nice to relax in. I would also recommend heading into town and checking out the town square. There are lots of fun little shops.