I have a wii with Cios 36 rev 10 and it works with all of my games.
you do not need to update your Cios for the games to work.
My other wii has cios 38 rev 14 and it works exactly the same (all games still work) only difference is it uses a different usb port for your usb device.
both wii's are PAL, both on 4.2 with bootmii as boot2
it wont harm you to update though and if you do not like it you can install rev 10 again and it will overwrite rev 14.