They need:

The Body Book!

I bought this because all in one week my kid slapped a preschool parent’s ass AND mislabeled my “boob” as my “stomach” (to be fair, there isn’t much delineation there these days LOL). Don’t wait until their kid (or yours) is slapping asses and mislabeling body parts. Get it now! (BONUS: The cool acetate overlays let you see different bodily systems, one atop the other!)