Our group started when an other playgroup from a college about 1 hr away demonstrated the game to the males of our youth group (after the actual youth group meeting. And it just happened that only the guys were interested for us.)
They basically had a deck made up for each prospective player and we had several games going, mostly one on one (newcomer vs. experienced player). There were even unlimited booster packs given liberally (because to a newcomer, a free pack is a free pack).
Looking back, the group from the college did a great job.
It helped very much that one of the experience players was also a former youth group member and he basically "planted" the group here- overseeing all questions, rulings, and even the card supply for at least 6-9 months. You will need to find someone to take a similar role who can teach basic strategy and deck building as well as promote the game itself.
I don't know how well you know the folks in the churches you mentioned, but I don't know how successful a cold call would be received. I would start with one or two people that you know in each church and see if you can make inroads that way- through some kind of relationship.
