"Just don't forget why they are called Folk Clubs."

Kendall is right. There's folk in there and they want to be entertained and get away from many of their cares and worries for an evening. YOU can help them do that. If you do, they will become 'fans' of you and your music. And one more remark from me before I leave this thread: NO ONE ever died from a bad performance. They are part of the business, part of the learning and part of the process. GO DO. And above all, have fun.