BJJ+Muay Thai+What? I need Help to choose!?

Well since you said there was 3 people BJJ wont any good because thats mostly ground stuff and that wont be of any use against 3 opponents. Muay Thai is where you want to be, clear and pin point striking. May I recommend you clinch up with ur attacker and knee the crap out of him Anderson Silva style. Go to youtube and type in Franklin vs Silva (the first fight) and you know what I mean. After your done with him the other 2 will be delt with percise striking.