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 Pratchett...no-one is finally dead until the ripples they cause in the world die away... The span of someone's life, they say, is only the core of their actual existence.
Terry PratchettI reckon responsible behavior is something to get when you grow older. Like varicose veins.
Terry Pratchett