Thank you everyone this has been a great help.
Firstly yes my plan was to sing in the performance as well so I'd have a sound check then press record and run over. I'm interested in the M/S spot for the piano although i've never used a M/S spot in this application before so I wouldn't know how I would mix it. I was thinking of setting up the ORTF pair first then seeing if I needed an ambience mic or if I should just use the cm47 and ribbon on the piano.
I will post some audio clips next week