Good points Paul. Sometimes a smaller setting is a good thing though as small groups don't get to perform in public a lot and run an aux mix to try to get a recording. They may not put the guitar amps and drums in the house mix but they might mic them and put them in a mix for recording. If you can get a feed from that mix, it may be usable.
To your point though, before you ask for a feed, ask what's in the mix(es) available to take a feed from.
My strategy has been to take a feed into the line inputs on a portable recorder, grab a live recording with the mic inputs (I put a stereo mic pair up on a single stand in the best location I can reasobably use) in the same portable recorder and capture audio in each camera. I need audio everywhere anyway to make syncing the tracks easier plus I get choices / backups. I guess I should've said "and", not "or" in my original comment on using a Zoom, Tascam, etc. with a feed or with mics since that's what I acutally do.
