I'm with Ian D on this one - for an "introduction" package (especially one designed for longevity, as I get the impression this is), it's best really to concentrate on evergreen classics (such as Yvonne Baker, Bobby Hebb, Patti/Emblems etc) - sounds that you'll hear out, or tracks sounding very much like them, maybe not every week but certainly every so often.
The trouble with going for current in-demanders - as some posters here are suggesting should have been done - is that they're likely to fall out of favour just as quickly - case in point, 12-24 months ago DJ Genesis "Tonight" was unavoidable - now it's forgotten: likewise only 5 years or so ago Bettye Swann "Kiss My Love Goodbye" was a guaranteed spin at most soul nights, now it's back to forgotten oldie status and hardly ever heard anymore.
As always - this is my opinion, I'm not always right