I have no idea if it will work for a child, other than to scare the pants off her, because I am responding to it so entirely on a professional (if nonverbal) structural and narrative level that I can't even begin to access it simply as a viewer. In any case, for me, it succeeded admirably on many levels, most of them visceral, thematic, and symbolic rather than strictly narrative. It is, for me at least, almost impossible to articulate how those successes work, but I will say that throughout the movie the audience I watched it with gasped, laughed, and--at the end--applauded.
I can also say that throughout it, I kept nodding and thinking this, yes. And the moment that crystallized that most for me is where Max explains to Alexander exactly what it is that is motivating Carol, and in so doing achieves a revelation about himself.
We don't want to want to be scared and lonely, and when we are scared and lonely, it makes us feral and mean. Such a simple thing, and so hard, so very hard, to show, to accept, to explain.
It's macabre and terrifying and I am a little concerned about what became of Richard (!), and my favorite moment (predictably) is the bit in the desert with the dog.
Well done, and I expect I will be nominating it for a Hugo next year.
Spoilers in comments, I do not doubt.