what do you mean by can't acess it because wrong region?
is the menu on janapese and you can't understand? i have a translated japanese manual which you can use to guide...
http://sheylara.com/wii/wii_system_settings_translation_v1.0.pdf
heres the translated manual.
you only need the mac adress for wilbrand\letterbomb.
maybe you can use other game hax? like batman\smash brothers or others?
if you can't access settings.. you can't also use homebrew to display that information..
2 ways you can get it without reaching settings or homebrew:
1: you open the console with a screwdriver and look for stickers inside that contain the mac address (not sure if wii got that stickers, usually latptops have..)
2: you connect the wii to the internet and with a computer you use a wireless hacking tool (like kali linux, or other wireless sniffer) to scan for wireless devices...