Most of the deluxes take five-we have 3 kids also. I know the BC, YC, BWI, GF, POLY, CR, all sleep 5 comfortably-2 queen beds and a day bed. We even had enough room in our standard size BC room for a full size crib several years ago. I was expecting a pack and play, but they brought me up a very nice full size crib with crib sheets.
The WL only sleeps 4 in a room, unless you book the deluxe room/suite thing. I know it's more than a standard room at the BC or YC, but I'm not usre how much more.
You won't be able to put 5 in any value room except the allstar music family suites. The value rooms as well as the moderates only have 2 double beds and sleep 4. The exception to that is POR. The Alligater Byou section has rooms with 2 double beds and a pull out trundle bed. It's pretty small. I'm sure you can find pictures of it on Allears.com
Your only other option is to book 2 rooms at a value or moderate. Booking a 1 bdr DVC villa through CRO with 5 people, as someone pointed out, can't be done. Plus, a DVC 1 bdr villa only has 1 king bed and a sofa bed. You could book a 2 bdr DVC villa through CRO, but it will be more $$ than a deluxe hotel room.
You can also put 5 in a room at the Swan-probably the dolphin too, but I'm not sure though.