Well, I'm not sure what to do. We could still have a mafia game I suppose but with it being so small, the question is do you have one mafia member or two. From past experiences, when we've had a small turnout like this and had 2 mafia members, the mafia invariably seems to win. That's because there isn't much for voting patterns and the game can be over in 3 - 4 days. Just putting in one mafia member means it might as well just be the killer role. We could do a game of just trying to hunt out the killer but that isn't exactly mafia.
Of course, we could also just put a hold on this game and try again in a month or two and see if that gets more response. What do you players wish to do?