The Handsomest Drowned Man in the World could be used as a story that can be told to children but, knowing Gabriel Garcia Marquez's choices for intended audiences it is hardly true that children were his primary target audience.
However, you can argue that the story possesses certain characteristics that are quite unique and appeal to the primary traits of children: Naivete, innocence, and the want to care for others.
The story also uses literary techniques that are appealing to children because in the genre of magical realism (to which this story belongs) there are situations that appeal to fantasy and the supernatural. Marquez, however, has the unique magical touch of making these fantastic and supernatural thing charming and told from a loving perspective that would also appeal to a younger audience and an older audience alike.
Yet, for it to be labeled as a story for children would be to reduce the theme of the story and all of the symbolism within it. I would, instead, re-state how the story can be intended for a younger audience for its fairy-tale consonance, for its indulgence in magical realism, and for the main idea which is that everyone has a capacity to love and care for things, even when they did not think they would be prepared to do so.