I hope all goes well for the recording. Have you considered taking a direct line from the PA to the recorder? I have had a friend coming out to record a couple of our band's gigs recently and we have been giving him a direct line out from the PA. The bass player also is feeding the digital recorder a direct line from a post EQ compression line out on his bass rig. The guitars of course are recorded from the amps speakers.

But recording everything live from speakers can work well if the mic placement is good. Doing a good live recording is always a challenge.