Here be monsters
You might have other issues getting your munchkins to sleep. Do you have to check under every bed, and in every wardrobe, for the monsters they’re convinced are hiding? Sometimes, calm and logical explanations are useless in the face of a child’s anxiety.
So having this little trick up your sleeve can help. Take any cleaned out spray cleaner bottle, fill it with water, and label it “monster spray”. Now all you need to do is go around the bedroom, making sure you’ve placed the monster repellent in all the right places.