I would like to recommend several songs by a somewhat obscure female group from the Washington D.C. area, Connemara. I don't know if they're still together, but have several of their C.D.s from a few years back.   They do a mix of instrumentals and vocals; good arrangements and harmonies. I particularly like their vocal of The Scholar, which takes its melody from the traditional tune, slows it down a little and gives the tune a nice spin with the somewhat contemporary words. I think this one would fit well into a session such as you have described.