Did you share out the various calendars to the users? If not, give that a try. Then they will get a list of calendars on the Calendar tab in the Web UI, and can assign a different colour to each calendar. Events from all the calendars will appear on their calendar, all nicely colour coded. And they can check/uncheck the calendars to view only the info they need at that particular time.
If you aren't using shared calendars, why not?
