Also remember Laura that if it's a concert setting they may well be the only act, or possibly the second of two, not really a problem.

However if it's a folk club type gig, you are not sure what your friends will be expsoed to before J & J so (and this is not meant as a reflection of the quality or standard of club singers in general) even if your confident they'll enjoy J & J they may not be prepared for the build up.

Still, in at the deep end eh, go for it!