Your Wii has 2 firmwares:
1) The Wii´s own firmware - Which you should always update using WiFi (safest)
(... the Wiikey allows you to override the region of Wii games. Bricking happens when a different region Wii game with a newer firmware update than what´s on your Wii is allowed to installed the update.)
2) The Wiikey´s firmware - Best place to get that is from their page (http://www.wiikey.cn/).