I actually just sang (and recorded) a choral concert this afternoon using my CM3s in NOS. Our performance could have been better but I'm quite happy with the recording so far. I'll post a sample if anyone's interested.
Your setup idea sounds good - I've never heard those Rode omnis, but the DPAs certainly are great for what you're doing. Your NOS pair on their own might be all you need, but if there's organ involved you might want the additional bottom end from the omnis. You also may not need to spot the piano either if your main setup is fairly close, but you have the extra channels so you might as well go ahead and decide later if you keep it.
I think your most important factors will be:
1. Will the choir PA be used for this performance? (Hopefully not, otherwise you're going to have to set up really far back to get any decent balance. It's probably just there for the church's "home" choir. And that many tenors don't need any more volume!)
2. Don't assume the choir will be in the loft just because it's there. Get in touch with the conductor ahead of time to see what his/her plans are. Some of the churches I sing in have choir lofts / stalls for the church's own choir, but we never use them, and instead sing in rows or arcs in front / back / to the sides of the altar.
3. Where will the conductor be positioned, and will the accomodate a tall stand fairly close behind them? And more importantly, is that the best sounding location for your main pair?