Both young and old -- parents included -- can have a great time at the zoo. Better yet, many zoos sell birthday party packages that cover food, activities and admission.
The San Francisco Zoo, for example, can accommodate a party for up to 12 guests with lunch, cake and ice cream, a train ride, zoo admission, free parking and a commemorative T-shirt for the birthday boy or girl. They take care of the setup, and perhaps more importantly, the cleanup.
If you don't live in a large city with a zoo, don't worry. There are plenty of other animal-themed destinations that could fit the bill, including aquariums, nature preserves, farms and petting zoos.