John,
If you are running ArubaOS 3.3.2.9 or higher, at the Virtual-AP (think SSID) level, there is a knob to drop broadcasts and multicast (Broadcast Filter All). If you enable this, users will not be able to find each others itunes sessions, and it will stop a good deal of the sharing, if not all. Just make sure you don't have an application that depends on broadcast discovery of clients to function before enabling this.