The best deal for tickets is through Goldstar. Pay just $15.45 for kids and $19.19 for adults, through May 2015, though there is a service fee. This weekend only (Memorial Day weekend), military families can get up to 4 tickets for just $10 each.
If you're going to be in the Philadelphia area, you may also like:
And be sure and follow my Mid-Atlantic Family Trips board on Pinterest.