Your Wireless LAN SSIDs can be associated to specific VLANs. Clients who
connect will issue DHCP requests, tagged with the VLAN associated to your
WLAN SSID. Each client VLAN used, must have a DHCP server to provide IP
addresses to that subnet of clients. Each DHCP server can specify different
DNS servers, in the offers to those clients.
So the answer to your question is yes, the subnet DHCP server that provides
DNS addresses to your wireless clients, can point to an OpenDNS host. I have
not personally experimented with parental controls, but you can direct chosen
wireless users to your choice of DNS.