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 PratchettRincewind had always been happy to think of himself as a racist. The One Hundred Meters, the Mile, the Marathon -- he'd run them all.
Terry PratchettIf you really want to upset a witch, do her a favor which she has no means of repaying. The unfulfilled obligation will nag at her like a hangnail.
Terry Pratchett