I would avoid the disco and dressing up! Not my scene and I am old enough and bolshie enough to tell them a firm 'no'. Team building NOT!
Make sure you keep hydrated and if you are too tired, then sit out. No one will die ;-) and in the Big Scheme ? If you tell them in good time then it will be accepted. Don't be wishy-washy about it, a simply 'not taking part' should suffice. Any idea where to yet?