Recording the group in an excellent hall would be great, I'd say--you really can't get enough of "lush" and "sweetening" if it's girl group, especially with alot of "spish, spish, spish" cymbals style vocal effects, and "wow, wow" electric guitar-style vocal effects that some of these groups do.
They will know exactly how they want to put it all together--if you can encourage them to really let loose, you can have one powerful performance on your hands!
I'd set the '57's up in a row, and the "soloists" can walk up to them. The rest should be about four feet back, in a semi-circular row, and then you need a pair of some kind of nice tube mics-- like Sputniks would be good for this-- as a spaced pair to take in the whole scene. Or a pair of sensitive LDCs of some stripe.
Maybe the Rode with a more-or-less matched significant other? I can't believe I said that....