The most difficult part will be to get the balance between organ and choir right - especially if the organ is beside the choir (and not behind them). And: if they are on a balcony, it might be difficult to get the mics where they would be best.
Depending on the room, I'd choose a spaced pair out of:
- Neumann KM130 or 183 (maybe with SBK eyeballs for a little focus, you can balance choir vs organ by pointing them more towards one or the other)
- Schoeps MK21 (love them as choir spots, give a bit of shine)
- Schoeps MK4 (if too reverberant)
- probably Schoeps MK2S, which I'll compare to KM183 in July.
- others here will recommend Royer which I've never heard and thus won't comment on.
- I don't think I'd use MS for that kind of music. I don't want the image to be very precise, but I want a very spacious sound. That's imho best achieved by spaced setups. Matter of taste.
Microphones always make me sound louder and better! -- Guitar Girl