That's a pretty interesting idea. Working in the Victorian Public Service, I can tell you that a lot of the people around me haven't a clue what goes on when I head out on the weekends to clubs and parties. I guess if they're open-minded enough to want to see for themselves, it certainly can't hurt.
Instead of a Friday night approach, I would personally take them out on a Sunday morning, but that's just my scene I guess since I don't go to rave clubs.
From my point of view, what you have in the Melbourne scene in terms of drug use, and these are generalisations of course, is Friday nights are younger kids in their late teens, early twenties, usually working part-time or studying and generally drawn to the hard trance/hard house clubs. Saturday nights are more mid to late twenties, working full time professionials; accountants, business-types, IT, call center workers and nurses and more often drawn to house/commercial clubs, also more often seen at day clubs on Sunday mornings in the Prahran area.
The first crowd you'd see more pills and speed, the second you'd see more coke. Though G is generally as popular among both groups, if you really want to see lots of G though (or any drug for that matter), the gay scene is the best place to go.
Personally, I don't envy your task, but it sounds like fun