The Austin Zoo, is definitely not the greatest zoo I have seen, but it's all we have in Austin, so go for it. The animals consist mainly of rescued animals, so I do have to give them credit as that is a very worthy cause. If you have young kids, I don't think they will really care that it's not the size of a regular zoo. They will enjoy it just the same. The older kids are a different story. They were not impressed with it and were quite bored. One thing that everybody did like was the train ride through the hill country.
Do be bring your pocketbook as it is quite pricey. Their souvenir shop is just as pricey as a souvenir shop at a regular zoo, and so are their admission prices.