As always, Shen has a very detailed report of what helps. Thanks for being so helpful to members, Shen!
I usually add fountains, kiosks, and tours for guests. For kids, the Splash Fountain and Face Painting kiosks, as well as the playground equipment, are always nice. Think about what you would like if you were at a zoo. OF course, entertaining animals are always the best, especially animals that children like to imitate. Moose, though they are cheap, are big hits with the kids. Bears, monkeys, and big cats are also very entertaining. Remember that endangerment level has little effect on how much the people like the animal, generally.