>>1562815If you live in the valley, you have some nice national bird watching centers I believe, I would take advantage to see some of those. There is also Goose Island state park near you, and while it is a car camp spot and highly crowded, remember that state parks allow fishing without a lisence, so that’s a fun day trip apportioning as well.
As far as camping go, I would definitely hit up Goliad. Beautiful heavy wooded trails, amazing bird life, and some fantastic mission church ruins to see right outside of the park if you are interested.
The next closest areas too you are a good three hours away, but worth it. Palmetto is gorgeous, and has some unique plant life plus it’s known to have a Bigfoot allegedly.
Guadalupe river ( pic attached) is another somewhat close to you park that’s worth seeing. Beautiful clear rivers and if you walk the shoreline, you can occasionally find fossils in the rock faces by the streams.