There's some things that you wouldn't tackle in a children's book because it would be beyond, not the mental capabilities, but the experience of someone under the age of say ten or eleven to encompass. But that field is smaller than you might think. They can easily cope with death and things like that; they know about it and it's a subject that often preoccupies them.
Terry PratchettPeople were people, even if they had four legs and had called themselves names like Dangerous Beans, which is the kind of name you gave yourself if you learned to read before you understood what all the words actually meant.
Terry PratchettI dare say that quite a few people have contemplated death for reasons that much later seemed to them to be quite minor.
Terry PratchettAdventure! People talked about the idea as if it were something worthwhile, rather than a mess of bad food, no sleep and strange people inexplicably trying to stick pointed objects in bits of you.
Terry Pratchett