I have some (limited) experience in this area having run a couple of concerts over the years. I obviously know nothing about the scene in Ontario, but the best advice I can give, particularly if you want to raise funds for charity is keep the expenses to a minimum and don't budget for a full house. If your venue can hold 90 then pitch your ticket price for a crowd of about 40 and work out a budget accordingly. That way if you do get a good crowd you'll be pleasently surprised, but if people don't come along you won't lose out on it.