Hi Emily,
Love the St. Louis zoo and have been there often. We also visit our local zoo many times a year, but never miss the chance to enjoy Disney's Animal Kingdom. It is so much more than a zoo.
You will find animals at Animal Kingdom, lots of animals, but Animal Kingdom is an enviroment where the animals live in a habitat almost indentical to their home and it still allows the guests a chance to learn and enjoy the animals. The park is a great mix of theme park thrills and the wild animal world we live in. There are a couple of thrill rides that your children may want to skip (Dinosaur, Expedition Everest and Kali River Rapids), if that is not their thing, but there are still plenty of things to occupy your time, like amazing stage shows that should not be missed( Festival of the Lion King and Finding Nemo the Musical). There is also a fun 3D movie located inside the Tree of Life named appropriately enough It's Tough to Be a Bug. The Kilamanjaro Safari ride takes you out onto the savannah for an up close view of the animals-be sure to have your camera ready. A great place to take the kids is Rafiki's Planet Watch. Here you will find live animal encounters and hands on activites..
Animal Kingdom is full of hidden paths that lead you to breath-taking views of many animal species that you may never see in your local zoo. Then for some crazy family fun, wander over to Chester & Hester's Dino-Rama in Dinoland. Here you will find a roadside carnival complete with games and prizes. Just a few steps away is the Boneyard where the kids can crawl, climb, run and slide themselves silly while you take a break.
It really is like no zoo experience we have ever had and has given us the ability to see and learn about animals we had never encountered. You can find additional information about Animal Kingdom
here. I think you and your kids will have an unbelievable time!