This is purely speculation, so apologies if it doesn't work.

You should be able to unbind all the necessary combinations on one character/account (I don't know of anyway to do them all in one go, so it will need to be by clikcing and unbinding each).
Then you should be able to go into your WTF folder in the WoW install and find a 'keybindings' file in there either at the account level or at the individual character level.
Copy this to the alts that need rebinding and they should get the same settings as the one you unbound.

As I said I'm not entirely sure if this works, but once I messed up all my keybindings on an account and copying this file over from another reset them (though possibly there's a 'reset defaults' option that I was too stressed to notice).

I'm pretty sure there's a way to unbind at least one key setting (as I've seen guides to disable caps lock or the windows key), but I don't have any idea how.