It's possible, but it's tight.
We stayed eight nights in 2005 with two adults, a 2 year old, a 6 year old, and an 8 year old. The two year old (who was nearly three and long since out of a crib) fell off the bed and hit his lil head on the night stand, the 8 year old and I tossed and turned (and fought for covers) all night due to lack of room on a double bed, my hubby barely slept due to fear of knocking the lil guy off the bed again, and the 6 year old happily slept on the trundle.
Shower and changing time stunk. It's hard to get five people, who are of different sexes and all modest, changed and clean in such a small space. We only have one bathroom at home, but we have our own rooms to change in. Privacy is a problem.
We love POR but will not stay there again unless we could afford two rooms, which we cannot. Next year when we return, the kids will be three years older and three years bigger. We need more space. It's either SOG with their huge rooms, queen beds, and sleeper sofa, or two rooms at POP. The details for the 2008 dining plan will be our deciding factor.
It's very personal. It works for many families, but we didn't like being so crammed. It's too bad. We love absolutely everything else about the resort.