Most of the deluxes have a fifth person option. We've stayed at the Poly, Contemporary, and AKL (deluxe room). I think that the Grand Floridian has the daybed, too, and the WL had deluxe rooms that can sleep 5 (I don't think they have daybeds in their standard rooms). I'm not sure about all the Epcot resorts--I think they have daybeds, but they might not be true twin bed size.
Also, at Port Orleans Riverside there are some rooms with trundle beds that can sleep a 5th person if they are young (I think the general age is 9 or under, but that would depend on their size). Also, the Fort Wilderness cabins sleep up to 6.
How old are your children?
T&B