No. He wants another WLAN, not full 802.1Q tagging/trunking nor router port based functions, ok lets say the main AP is on 192.168.1.1 (br0) and you add a virtual wireless interface (br1), bridge br1 to a different subnet like say 192.168.2.1, this is just multiple wlans using one radio on the same interface.
With a VLAN setup, you'd unbridge one of the physical ports on a router, assign that port a different IP/subnet, plug in another wireless router that would be on this VLAN, add an 802.1Q tag/trunk to this new VLAN so it could pass traffic through to the internet on a whole new layer 2 control, which is not what i believe the OP wants here. And also to add, Atheros with dd-wrt doesn't support physical port mapping VLANs, so if port based group switching is what is needed here, you'd be outta luck...