Well, as far as I know, a 2 year old doesn't need a ticket for the parks. I think that admission charges start at 3. I know that the day my son turned 3we purchased his AP. I truly believe that honesty is the best policy, and feel that lying about a child's age sets a poor example for them, so to me it would be a big deal.
As far as dining, we have only spent single days at the park (we are local), no overnights, and have always used CS, so I don't know the rules there.
Just my 2 cents, of course.
Have a wonderful time on your trip!
Amie