This is what i did but on the router. I have openwrt on the router. You can install an extension called PBR (policy based routing) on it.

Then you set up one wireguard interface that’s in the same firewall zone as your LAN to your lan and another that’s in the WAN. You can create policies to route any outbound connections (including the ones from your mobile client devices) through the commercial WAN wireguard connection.