In shows aimed at children, a lot of the time whenever it delves into “spooky” territory, there is a lack of any true scare factor, or the idea that anything could hurt you. It is played safe, the plot is typically tame but revolves around an environment steeped in halloweeny atmosphere.
Some of the most iconic shows known for this sort of thing are those of the Scooby Doo franchise, which acted as an introduction to many kids to the visual beauty of horror, even if a lot of its many iterations weren’t very scary themselves.
Walt Peregoy was responsible for a lot of the background art in the show Scooby Doo, Where Are You? and helped in establishing the iconic creepy mood of the areas explored in each episode. He serves as a massive inspiration for my own background/environment design.
When it comes to horror specifically made with children in mind, I’ve found that you can split them up into showing off something conventionally scary, and having an underlying horror that reflects a situation that could very likely be happening to a child watching. For example:
Visual Horror: Big scary spider lady wants to steal your soul and sew buttons in your eyes!
Underlying Horror: The anxiety and loneliness that comes from moving to a new area and away from what you know and love
Visual Horror: Big scary monster kills kids and turns them into trees!
Underlying Horror: A shift in the family dynamic (Greg is Wirt’s half brother, he’s significantly younger than him and Wirt continuously takes out his frustrations on him. It is never explained if Wirt’s dad passed away or his parents got divorced, but we know for certain that his mother is remarried, which is something that happens in a lot of kids lives and brings about complicated feelings)
These examples also have a fairytale-like quality to them, with the main characters learning something through the horror they experience. This in turn teaches younger audiences the same/a similar lesson without putting them in harm's way.
Horror can be just about anything. If executed correctly, it can act as a means of helping one deal with their own worries or sorrows. Children for the most part have less to worry about in their lives than adults, but it doesn’t make their plights any less valid- horror that takes from the things that can bring about uncertainty in a child’s life understands this.