I believe it would be fun if in the Sims 4 game when they hear a loud thunder the sim kids would run to grab their closest parent legs, scared of the thunder noise. If their parents are not available in the room or in the lot, they would grab the legs of the closest adult or teen.
Kids should also be able to prepare simple food, and play with baby sims.
And now with toddlers, I guess it would be a great time for players to have preteens like suggested here:
https://forums.thesims.com/en_US/discussion/comment/15147389/#Comment_15147389
Comments
Children are able to prepare snacks using the microwave. They have two interactions with babies: Coo at and Talk.
But to your idea, I would like to add hiding in the bed, walk-in closet, and avoiding windows and electronics.