Vlan setup with DD-WRT on MT300A

I am trying to use the MT300A in client mode-like setup for a more secure hotel wifi intermediary between the public wifi and my computer. I have successfully installed DD-WRT (as recommended in the GLI wiki) and have it working as a client with openvpn…but what I want to do is use it in the same manner but without using the ethernet cable for my LAN. I have searched and it appears that this version won’t support port-based vlan, and the GUI appears to confirm this by not offering the setup -> vlan option. Reading up on how to enable this via telnet and editing the nvram directly has me confused as well. Basically I want to use a public wifi as the WAN, and also have my MT300A be a wifi vpn’d AP for my devices.

Router Model
Buffalo WHR-300HP2
Firmware Version
DD-WRT v3.0-r29218 std (03/07/16)
Kernel Version
Linux 3.10.99 #1733 Mon Mar 7 08:49:10 CET 2016 mips
Any help or recommendations?