T.T.
We just took our daughter to San Antonio and she had a great time. She loved Sea World and there is a zoo there - although we didn't go. We went to Sea World 2 days and then went to the River Walk and ate at Rain Forest Cafe (the one here is just too far - so since it was convenient we went there).
Hyatt Hill Country is a very nice resort (kid friendly) and it's right across the highway from Sea World.
This trip was great - my daughter was about to turn 4 (just 3 weeks later). You could fly on Southwest and I think it's an hour flight (it was a 5 hour drive).
Good luck!