I think they want them taken at an event, so more of a "lifestyle" portrait rather than a studio/executive style portrait. So i'm thinking a two/three light setup at most. Main, fill (might just use a reflector for that) and a rim/hair.
Honestly I'd charge somewhere in the neighborhood of $50 each. I'd shoot at least 3 frames each. Then again, my time is most valuable to me and if I'm going to take on a photographic assignment I'd want it to be worthwhile. I'm not trying to build clientele.