The great thing about Stephen is that he sees the movie as a separate thing, I think. He wants it to capture the essence of the book, and if he feels that's been done, then he's not too particular about the details. I think that's why he's happy.
There is another thing about a kid, if we all remember, that you have an attraction to evil. Evil is exciting and evil is interesting, and plenty of kids have a fascination for it.
They were using the dolls to project their dreams of their own futures as adult women.