You can simplify even more with just one single parent and one single kid restrained by the cable set in a scene within a single location. Whenever the kid wanders a little too far off he will be pulled back… center the story around the feeling or emotion of the toddler and think of a way how the cable can be snapped or broken. When the toddler is lost, the story will be about how the parent response, in anxiety and panic. The kid actually comes back on his own to the relief of the parent. And they are united. Happy ending. (Just a suggestion)

https://www.youtube.com/watch?v=QugooaNRnsk

There is something you can watch for inspiration.