Basic Bonjour on IAP with network-assigned IP addresses would work, if the Bonjour devices are in the same vlan.
But, guest ssid clients are treated separately in a private vlan, such that they don't see any mcast from network devices; hence, does not work with external bonjour clients, unless the bonjour devices too get IP from the ap's internal guest-vlan.
That said, we are working on designing and implementing a distributed algorithm in IAPs for enabling Bonjour device discovery across vlans. We are targeting beta by Aug, and a full FCS by end of the year.