I've got a better idea --- let Pope Pius XIII go to this event, offer the Traditional Latin Mass, and call these young people to a life of modesty, chastity, avoidance of near occasions of sin, reminding them of the Four Last Things and how horrible it would be to die in mortal sin. (But first you'd have to teach them what mortal sin is, and call it mortal sin, not "grave" or "serious" sin. They started changing the terminology in the late 1970s, and my BS detector went off immediately.)
A short course in traditional Catholic doctrine, with emphasis upon the Sixth and Ninth Commandments (surely the way most of these young people fall into mortal sin in the first place), also wouldn't be a bad idea.