I don't know what ship you've worked for, but Carnival and all of the brands under their line as well as Royal Caribbean and all of their affiliates utilize Promo Only, the same music subscription service that radio stations and my company uses. This provides the ship with current music well before it hits the charts and ensures they have a good music library. Most larger cruise ships have reformatted their booths to be capable of utilizing Serato systems.
What relevence does this post have to the teen cruisers who will not likely be participating in any of the nightclub activities where the staff DJ will be present.
Finally, advising guests to consider giving music to other DJs is really both unprofessional as well as illegal for all intensive purposes.