You won't convince reddit-tier atheists with any arguments at all.
Honestly, just act in a very Christian manner, polite and understanding, don't preach in an aggressive way, don't be afraid to back down if you have no argument. You don't even have to come out with it out of nowhere, maybe wait for a better chance and reveal your power level to each friend separately.
Key is not to lose your friends or come off as a prick so you may be able to convince them later with your good deeds and great faith.