a "hand flag" (small flag that can be held with one hand, such as those used for signaling or flag semaphore)

play, amuse oneself, enjoy oneself / spend one's time idle, do nothing / for an item not to be in use, be spare or idle

park

to shake; (of a hand or flag) to wave; (of a tail) to wag; (of a baseball bat) to swing; to move something back and forth in a circular motion

child

swing, wield, flourish, wave, shake

assuming the air of, acting like it (when one is not)

flag semaphore

plural of 子供: children

child's naive mind, child's juvenile mind