I'd say that the characters are talking animals would be the most likely hint that the story was made for children. This is because most movies/plays/cartoons feature at least <em>one </em>talking animal, from my experience, and everything that happens in the it would be fictional. Yes, the story might be realistic, with only some fantastical elements in it, but it would still most likely be written for kids. Snow White and the Seven Dwarfs, Cinderella, Sleeping Beauty, etc. etc, are all solid examples. Hope this helps! :)
