With four in an inside cabin, I would pay additional to have a larger cabin...you and your boys will need every inch.
You can check other Internet sites which specialize in offering contracted rates, which are sometimes less expensive than the cruiseline directly.
Cabins I would check out:
Deck 6: Deluxe Ocean View (sofabed)
Deck 7: Family Ocean View (two sofabeds)
The extra room with the veranda will definitely come in handy!