Timing can be important for a Dinosaur Valley visit. The high point for my granddaughters was walking in the dinosaur footprints in the rocky river bottom. This works when the water is low enough, which will be most of the summer after the rainy season is over. But this is down in a ravine, and when the water is high (after thunderstorms upstream) it gets really high.
We liked the park and the campground, the kids did not much like the heat (100+ daytime, high 90s at night).
We visited Mustang Island in the winter, investigated the state park campground, chose to stay at a more developed RV park in Port Aransas, walking distance to the Pass. At the time we were there, we had a strong steady onshore wind along much of the coast. Although the RV parking at the state park is sheltered behind the dunes, the wind still comes over the top and keeps sand in the air.
The annual pass for Texas State Parks is worthwhile if you will be there for a week or more (that's how long it took to pay out for two of us). Texas has many great state parks, particularly the historical parks like Goliad and LBJ Ranch. If you have the pass, you'll be inclined to visit more of the park system. If you don't have it, you'll be passing them up because of the day use fees at each park.
Last time I bought the pass it was 12 months from date of purchase, so I usually picked one up first time visiting a park after the previous pass expired. But you might check that they've not gone to calendar year, as many other states have.