I have several AP's on different channels with the same private and guest SSID's. A sort of mesh network so to speak.
OpenWRT is the only DHCP server
I'd like to give devices that are coming in via the guest SSID an ip address that resides in a different subnet as to be able to be sure that access is only allow to WAN.
As long as you create the necessary vlans for guest and lan and propagate them to all connected devices, it is possible to have all your private and guest networks on all the devices.