A shopping centre will get about 4 or 5 APs for pay-as-you-go Internet access.
H-REAP was suggested however I noticed in,
Enterprise Mobility 4.1 Design Guide
under "Restricting Inter-Client Communication" that,
"Two or more clients, associated to a WLAN that is locally switched (by an H-REAP), are not prevented from communicating with one another even if Peer-to-Peer Blocking mode is enabled on the WLC. This is because locally switched wireless traffic does not go through the WLC.
Those H-REAP WLANs that are central switched have inter-client communication restricted based on the Peer-to-Peer Blocking mode setting on the WLC."
Since Central Switch which supports Peer-to-Peer Blocking would probably give crap latency, that probably rules out H-REAP for this applications.