What kind of information are you looking for, or what is your intended use?
One of the most basic way to do this would be to use SNMP to get the number of registered wireless clients out of each access points and generate a chart based off of that information.
If you are looking for this information to be available to the hotspot, can setup VLANs for each access point, and bridge all of the VLANs together. Then in the bridge set "use IP firewall" to yes. You then have access to what "port" a client is connected to on the hotspot. Capsman might also be able to provide this information, I just don't use it so I cannot say what information is or is not available.