Honestly, what are the flaws in my story? What are the weak-points?

It sounds like an odd story to be honest. Generally you don't see Tooth fairies and Barbarians in the same story. But I think it would make a good story. Kind of curious about why Claw decides to accompany her and why the ogre is after Toenail. As for being childish I don't really think of it as a children's book, most likely a tween book. By the way thanks for answering my question.