An Exocentric compound for Children

One suggestion would be buttercup, which is neither butter (though it is yellow) nor a cup (though I suppose the flower is vaguely cup-shaped).

The line between endocentric and exocentric compounds is not always clear. For example, word meanings change. Today, a footprint is neither a foot nor a print, but print referred originally to any kind of mark or stamp, and thus footprint would have been endocentric. In other cases, the component retains its meaning as a standalone word, but it is overshadowed by a more common usage. A screwdriver is neither a screw nor a driver, in the sense of driver as the operator of a vehicle, but then driver refers to something which impels, as a screwdriver certainly does. And many compounds are analogies to begin with. An oxbow lake is neither an ox nor a bow, but was named because it is the same shape as a type of collar for an ox. Still other words appear to be compounds, but are not: polemarch is borrowed from ancient Greek, not from the union of pole and march. And so there is room to argue about the suitability of words like railroad, doughnut, headphone, skyscraper, gumdrop, and many others.

For children, it may be good enough to stick to contemporary uses, in which case I think the following should be uncontroversial:

Animals: butterfly, dragonfly, firefox, hedgehog, polecat, seahorse

Plants/flowers: bluebell, catnip, forget-me-not, honeydew, pineapple, snapdragon

Objects/Materials: cardboard, dreadnought, matchbook, moonshine, sawdust, touchstone, turtleneck, wardrobe

People: birdbrain, egghead, litterbug, pickpocket

Activities: brainstorm, fanfare, hogwash, honeymoon, potluck, shorthand

Places: carport, speakeasy

Other: humdrum