...you won't have to fiddle around with reverb since you are recording in a church.
Don't be too sure of this!
I think the ideal is to record four tracks, with one microphone pair fairly close to the piano for clarity and another pair further away to get the ambience of the church. Then you can play around with different mixes to see what works best. If you're recording with just one pair of microphones, you should err on the side of having them too close to the piano rather than too far away: you can always add reverb later, but you can't take it away!
If you've got three days to record, then expect to spend a big chunk of the first day just playing around with different microphone placements.
Good luck with this project!