First of all, you'll probably NEED to use keyclone in order to NOT shuffle focus from window to other window.

Also, the G11 keys aren't always picked up by WoW (from my experience). What I had to do was use the logitech software to map one g key to some crazy key combination -- such as ctrl+shift+\, or other complex things you'd never press otherwise.

Then map that key combination to a bar on the 2nd toon -- and don't map it on the first. When you press it, it'll be sent to both clients, but the first client doesn't have anything mapped to it, so nothing happens.