Overall it's interesting, though like Mike said, If you hadn't explained the story, I wouldn't have any idea about what's going on...besides the basics like a girl finds magic book and turns some poor mook who's probably her friend into a child, etc
Try shading, I think it'll help, even if you're going for simplistic....
Faces are a bit sharp and angular at times, like with the witch.
I also think you should try squashing their faces a little, I find that sharp long faces are usually male characters, whilst softer smaller faces work for girls
Besides that...TEACH ME about drawing body postures! They're soo hard, but you're soo good at it!