I would call a travel agent and talk to them. Tell them your situation and how much you can afford to spend. The T/A will advise you better then anyone else can.
Personally, I wouldn't want my 14 yo son and 18 yo daughter bunking together as they would probably kill each other, plus no one under 21 can be in a room without someone older also occupying the room.
I have heard before that a suite might just be the ticket as it can accommodate the 4 of you more comfortably.