I think the above mention of "Sylvester & The Magic Pebble" is highky apposite in this conversation; all of William Steig's books for children have an inherent darkness in them, and while everything turns out all right in the end, the characters have to face some unpleasantness in order to get there. Older songs that are associated ion the modern mind with children didn't all necessarily start out that way; in fact, probably the majority didn't!

It's worth noting that most of the "classic" children's music/rhymes/literature of the 19th & 20th centuries are higly sanitised revisions of older versions(Grimm's tales, traditional songs, etc.), cleaned up for Victorian children. It's really not until the 19th centuryu that childhood as a concept becomes this soft-focus, romanticised idyll in the popular imagination; aand even then, it was the socio-economically fortunate few for whom this ideal bore any resemblance to reality!