I've got a Z-board for gaming - it allows you to insert different keyboard layouts into it for different games, but is perfectly adequate on the regular layout. Not sure if physically replacing the keyboard with something with a different physical layout counts as against the WoW rules, though (although how they'd detect it I don't know, and it strikes me as a rather silly rule, for what it's worth!)
http://www.amazon.co.uk/Ideazon-Zboard-Starter-Battlefield-Bundle/dp/B000MDXN0Y/... copy
As for a mouse (and also the keyboard!), you may want to get yourself 2 - one for gaming (a nice little precision laser optical mouse jobby) and a cheap and cheerful 2 button for the young folks to bash about.