Children ages 3 - 9 are charged the child price for park tickets. Children age 3 - 9 are charged child prices at buffets and can order off the child's menu at other restaurants.
Children 10 and up are charged adult prices for everything.
It is 3. If you are celebrating their b-day there, the child can be 2 when you start your visit without beign charged for an entrance fee (for the entire trip).
Here is another one that someone might be able to answer. Staying at a Value, I know it's a maximum of 4, unless one sleeps in a crib. Does the child under 3 apply to that too? Or do they mean an infant in a crib?