Ahh I'm jealous I'd love to be in your position and join these activities and take every opportunity to bring reason to insanity. I've done something similar in the past where I was the lone voice of dissent - takes courage and I did receive some unpleasantness at one point. However, my constant questioning at every opportunity and their 100% inability to give convincing answers did generate an atmosphere of embarrasement for them. At one point I was asked to just stay quiet and accept what the bible said - naturally I did not comply. And humming audibly as if bored and staring at everyone while they prayed also seemed to make them nervous.
Against such odds an essential tactic is never go on the defensive. You must always be the one asking the questions, as soon as they start asking you questions and you begin to reply then you will unlikely recover. If asked a question you must only answer it with a question. Remember that it is the Christians that are making the claims for their religion, your job is to make them see reason and for them to prove their case.
But it would help you were not the only one otherwise you will significantly feel the pressure of being overwhelmingly outnumbered.