For 5, I prefer a room that includes a dresser for storage (meaning, the 5th person can't be on a fold-down Murphy under the TV). Bonus points if there's a usable desk or table (not a table that gets folded away when all the beds are down) with one or more chairs, for eating. I know that most deluxe standard rooms (but not Wilderness Lodge, which only sleeps 4) have these features. Not sure about moderates/values, as I haven't stayed at any that haven't undergone a refurb since.
If you can do without a dresser (e.g., bring collapsible folding shelf units for the closet, or keep clothes in packing cubes that can be stacked in the bathroom vanity, or just live out of suitcases), then any of the DVC studios except for Beach Club (which has tiny, cramped studios with the folding table under the Murphy bed, rendering it largely useless for a party of 5 that will need to use that bed) would probably fit the bill, with those at the Polynesian being the largest (and offering an additional 3/4 bath, with additional storage!). Plus, of course, all of the DVC studios (except the Grand Floridian Resort Studio Villas, which have the "plus" of offering 2 proper beds plus a daybed, but the "minus" of not having a full kitchenette) having a kitchenette with mini-fridge, microwave, toaster, coffeemaker, sink, and counter and shelf space, which is fantastic if you're preparing meals or snacks in the room. We typically rent DVC points and end up spending less on a DVC studio than we'd pay to stay at a non-discounted moderate the same week.
The Fort Wilderness cabins were also a great option for families of 5 or 6, with sleeping spaces for 6, a dining area, and almost a full kitchen -- however, those are slated for replacement and it's unclear how the floorplans in the new units might change.
