I would choose something from Miles Davis to start them off. If they come from an easy listening type of background, I might have them start with Kind of Blue. You can't miss there. If they come from a rock and roll kind of background, I might start them off with Miles Davis live at the Fillmore, March 7, 1970. This rocks, for sure. Another choice might be Bill Evans, Portrait in Jazz, or perhaps something from John Coltrane, Blue Train.