uMMPPPP..........

a SINGLE MIC??? FOR 5 INSTRUMENTS and 3 Vocals..... not a job for a sound engineer!!!!!!

what PA system? - inputs/outputs etc.........

handy to have......

mixer/amp or mixer - amp

3 vocal mics (presuming instruments aren't acoustic)

DI instruments

one sound engineer

simple system..........

plug mics & instruments into mixer, vocalist sing into mics, intruments play (DIed) through PA - sound person mixes sound so it sounds pretty then records it onto Mini disk (overall effects can be added either during or after recording) make CD sell Cds make fortune...............

Why not get a local studio to record it? PI Link
as metioned in an earlier thead have a "mobile Studio" and I'm sure other "cottage recordist" could do the same - Good equipment is essential for a good recording - and as you appear to have very little it would cost far more to buy it than hire it and a couple of sound engineers (who whould also do the sound for the concert?

Good luck

PJS