I would describe the cushions as padded mats. Very similar to the pads you might bring with you camping and place under your sleeping bag inside your tent. I don't think they necessarily restrict how many you can request, so you might want to ask for a few.
Please note that when the sleeping bag is set out, you will have limited walkways in the room, depending on where you set it. There's a little bit of room to place the sleeping bag at the foot of the beds, a little bit of room between the two beds and some extra room in the entry of the room (although that might restrict access to the bathroom).
If someone doesn't mind sleeping in a sleeping bag on the floor, you won't have that much of a problem. If you are looking for it to be as nice as another bed, it won't be. If it is a concern, you might want to get two rooms or upgrade to a suite with enough beds for your party.
Matt