"The cong. is made up mainly of poor old people."
So, basically, you will be attempting to disillusion a lot of poor old people who have believed their religion to be the 'truth' for most of their lives and have NO outside moral support. Sort of like pulling the rug out from under them.
I don't think that is a good plan - from the 'inside' or 'outside'.
These old people have nowhere to go. Leave them alone. Live your life. Don't waste it trying to convince a lot of old people that they are wrong.
Of course... I don't believe you're real. I don't believe in the Easter Bunny either. (But, I DO believe in the Playboy Bunny... SHE's real! ;-)
Regards,
Jim TX