Garner state park is an awesome family park! I prefer to stay in the New Garner area because there is less people in river. The Frio river is very clean and clear. My boys and I use our goggles to chase catfish in the clear water. If you have a trialer/
RV you need book your reservation atleast 6-9 months in adavance. If you are tent camping you can get in almost anytime.
Chalk Bluff is on the Nueces river near Uvalde. The river there is also very clear and clean. You can rent canoes, paddle boats and tubes. You can also go horse back riding. A two hour guided ride was $25.00 per person. You can double up with little ones on one horse.
These two rivers are the cleanest flowing rivers in the state that I have seen.