Hm, dwarves probably wouldn't work as they aren't really Narnia specific. There's the Dufflepods, the people from the bottom of the world, the slavers and that kind of thing, but they'd be kind of obscure.
You COULD got the opposite direction of a group of four child crime bosses based on Lucy, Sue etc., I guess. And have then empowered by some vague demonic/godlike Lion whatsit or something.