The solution was not via snmp but via syslog. Both d-link: DAP2660 access point and d-link DSR-500 have basic efficient syslog support.
For DAP2660 the syslog server config is under status->log->log setting menu. Where one can state the syslog server ip address These syslogs will tell you which clients macs are connecting or disconnecting from the wifi
For DSR-500 syslog configuration is done in two stages: first configure the syslog server under Maintenance->Logs Settings->Remote Logging->Syslog. Then define which data will syslogged under several menu items under Maintenance->Logs Settings. One can determine various categories of events to syslog. among them dhcp messages and even http connections details.