For the 4-10 age group, my vote goes to Lowry Park Zoo. It is considered one of the best kid-friendly zoos in the country. Busch Gardens is an awesome park- with great animals and terrific thrill rides, and a new area called Jungala that would appeal to your kids. However, Lowry makes for a MUCH cheaper day, it is more of a true "zoo" and has a more laid-back pace. Have fun!