I looked into this option for our family of 5. I was told that deluxe rooms were not part of the discounts being offered right now but they would be happy to book me the room at $405/ night!!! I confirmed that the only difference in this room would be the addition of a daybed. I think this is outrageous, personally. It is the same situation at the AKL.
Your options for 5 are POR, or one of the other deluxes if your looking for one room, although I don't see any reason you shouldn't put your three children in one bed if you're comfortable with this.
It seems punitive to me that they would charge $10-$15 for an extra adult in a room, but you should pay $250 more per night for your three year old!! I know, I know someone's going to say "fire codes" and all I can say to that is, "give me a break".
We reluctantly decided on POR for our quick October trip and will be at the YC in February to insure the extra bed, but I would have know qualms about it, if I were you. Just MHO.