If you are feeling really bad, don't forget a black soul gem when offing the 'carls.

Decapitate and keep head on shelf. Atleast thats what i did!

excellant way is to type (in console) "tai" - that disables them, so they cant move or do anything then type "setscale 0" and they are so small you cant see them, then you have a invisable and no functioning npc!

but the most obby way is to just murder them, or tip them off a building or something :L