Same channel or different channel? I would assume different channels?You'll want to set up both as AP-Bridge with the same SSID and same encryption, etc.
This is not the solution. With metarouter my router's CPU gets horribly overloaded so much that my whole LAN starts lagging (RB2011).If you really need those features at the moment. Run openwrt image in metarouter and run ovpn from there with full feature set.