Clients that have a wireless interface are “up” but may not have “attached” to the wireless network.
The kernel will send 3 (by default) messages to an interface that is “up” before giving up, long before it usually attaches to a wireless network.
Hopefully this can be triggered on the server and client sides by a script poking a /proc parameter.
however, I think triggering a ra announce on a dhcp request is still a good idea.