The best of Halloween (if you measure the holiday by our actual practice, not it’s meaning) is dressing up as someone else, the theater of it all. But the theater is not all about the costume.
Even if what’s happening among very small children on Halloween is mostly butterflies, superheroes, and farm animals, there has always been an element of fear in this holiday. While this can be ridiculously age-inappropriate, there is a kind of scary theater which allows even the very young to act out being afraid, and that’s not always a bad thing.
Like peek-a-boo or jacks-in-the-box: the anticipation of surprise is a kind of developmental exercise that has its benefits. Through the enacting of shock and “fright” moments, a child can exercise the part of their mind that one day (hopefully not too soon) will have to deal with real fear. The game allows a child to notice their physiological reactions (adrenaline, rapid heartbeat, faster breathing), and to survive the stressful moment, ending it in the catharsis of a good playful yelp.
“Boo” games are a great hit in preschool, as long as they are not threatening or overwhelming: children learn early that Halloween is about “playing” scared. Of course too often they also learn that there are real frightening things in their world, and this one good reason why it might be beneficial to have a safe place where they can play out fears while maintaining control (the ability to say, “Stop”, to seek the comfort of an adult, to influence the script).
So while we have our reservations about the crazy and sometimes horrifying culture of Halloween, we recognize the joy of dress-up, and the very real benefits of this kind of theater game.