Do you run everything, guitars drums and what have you through the PA? If so then the previous suggestion of just record the PA output will work fine, otherwise it won't be a good balance at all.

If there's a spare person, a pair of headphones, and a extra mixer a separate live mix could be done, off the PA and mix in a couple of ambient mikes.

Very every session recording, maybe use any old stereo recorder, run the PA to the left channel and an ambient mike to the right. You'll have to run it back through the mixer to control the balance and it won't be swanky stereo, but it'll show whether you remembered the chorus right.

For this kind of thing the choice of mike is pretty academic, a good old 58 will do nicely, or whatever is spare! You will have to play with the position a bit, but it should only take two or three practice runs to find the right place.

Have fun with it!