+1 Plush
I would also be inclined to try the DPAs as a spaced ambient pair further off the choir, this really depends on the space. It's nice a nice option to have, and those mics will kill in that role.
Putting the piano in front of the choir may mean putting it at half stick to control the level, which I dislike doing. Much better to have it wide open, especially if using a ribbon on it , you'll have a lot of high end to make up with the lid down..
I personally wouldn't worry about the choir spots too much.
Let's hear it when it's done