For me this question would be the key point. The one thing that always runs through my mind in this type of scenario is WHO is in charge? If it is one Dom that is fairly simple, but 2 Dom's, who is the lead, are details worked out in advance, etc. And does everyone trust that person to be in the lead role?
*lol* I always have this vision of 3 or 4 naked people standing in a room with the common theme being "I don't care what do YOU want to do?" Think that would be a quick mood killer!