This isnt something i have tested with wow, but i used to use it on HOG (hidden object games) with 3 mouses when my mum, my gf and myself where playing them on a big 48' TV.

http://www.wunderworks.com/teamplayer/ - allows multiple mouses and cursors. - no idea about multi keyboards on same pc tho.

no idea if it will help or just complicate matters.

(i just woke up was browsing and have to leave for work).