That's a good question. I've been counting my 2 year old in our dinner reservations. But she's under 3 and doesn't need a park ticket. (Right?) (At least every time I check, it says children under 3 don't need a ticket.)
When I made my reservation, I selected my DD's age as 2. So I am thinking you do have to count 2 year olds and just note the age at the time of the reservation.