Nominated sound man's wife here (because he can't get to the computer at the moment and I'm a player in the band anyway!).

Richard: none of our instruments can be plugged in directly; our line-up is melodeon, concertinas and whistles/recorders so we have to use mics I think. We're unlikely in the future to have any instruments that can plug in (even with the guest musicians who are likely to join us) so need to allow for all mics.

Might be a stupid question (but we're very, very new to this) - how many mics before the sound starts to muddy noticably?

Rookies question no. 2 : how feasible is it for two instruments (the two concertinas, say) to share a mic?