This is a great place to spend with your kids. And...

This is a great place to spend with your kids. And if you make it on time for most of the shows and documentaries, it will add up a lot of value and information to the experience.
Animals are a great subject to study and what a greater place to start it if not at the Houston Zoo?!
Just consider to spend at least half of a day if not the whole one because there are so many thing to see. You may even consider bringing a light garden card / radio flyer cart to help your kids move from one point of interest to the next one. Everybody will be exhausted by the end of that day, but having a great experience.
Dare to plan it! Dare to go! And have a lot of fun!