Our job as writers is to create believable and entertaining stories for our readers. This is true whether you’re writing for children or adults. Details about the setting — location, time period, and everything that goes with it — are what make the story realistic. Research is part of the process. Writers need a clear picture in their minds to build their imaginary worlds.
The trick is knowing how much information to include without making it seem like an info dump. You might be interested in who the architect of a famous monument is, but more than likely, your reader won’t care. When including facts from your research, ask yourself if it moves the story forward. Does it establish the setting? Does it advance the plot? Does it help explain the actions of your characters? If you’re not sure, put the information into a separate folder and see if there may be a place for it somewhere else in the story. In the case of writing juvenile fiction, topics about the supernatural, or mythical characters may be of interest to the reader. Including them, even if they don’t directly move the plot forward, may be a good idea as long as they somehow relate to the story.
Readers care about characters. Your research should make them as realistic as possible. It’s fine to occasionally include facts and trivia, especially if you’d like young readers to learn something, but they should never take the reader out of the story. When including those things, consider how your characters will react to whatever information you provide.
Research is more for the author. It helps you know the facts so that you can be more of an authority when writing fiction. If it feels real, and it’s entertaining for your intended audience, you’ve done your job.