[urumita]

It's probably all over by now. Is this in a studio or remote? First you have to figure out where in the space you're going to place them, the best place is where it sounds best to them, find this first and then adjust it according to your needs. Second, how many tracks can you record and what's your delivery format? If you can record 16 tracks you'll have no problems in setting up enough mics. where you'd believe they'd be necessary even before the players arrive. My favorites are 1 omni and a crossed figure 8 almost in the center of the ensemble and various pairs of A/B omnis in different time alligned locations and a set of omnis that act as boundary mics. (as close to parallel walls and as close to the ensemble as possible, even behind them, BASS). You can put up 11 "ambient mics." and still have room for 5 spots, if it's not live to 2 or live to 5.1 then you can always listen, set delays and mix later.
There's always lots of [blank] flying around about how it sounds to you and how you should capture that sound but if you don't have any idea how it should sound then you're [blank] out of luck. Trust the advice of the musicians who know their music and sounds but don't give in to destructive egomaniacs. Capture what you can. Keep accurate records of the takes and edit points and attempt to make test edits for the ensemble to hear so they can remain confident during the recordings.