One more thought-- Really good musicians tend to get bored while playing for contra dances, and they know it's pointless to be a perfectionist, so they look for other ways to make it interesting. They're always looking for new tunes, new arrangements, new medleys, new musicians to sit in with them, and especially new instruments. So don't assume that better musicians "have better things to do" than to help you out, unless you've asked them-- and even if they do, you can always ask someone else.