The baby elites, or in layman terms; grunts, can often be seen taking point in various covenant military formations.
If and when you encounter a baby elite try to:
-Shoot for their soft, undeveloped skull.
-Hit them with a blunt object, this will dispatch them with relative ease and effect.
-Sneak up on them during their "nappy time" and use one of the aforementioned methods.
-Throw a standard fragmentation grenade at them, their shattered hopes and dreams of becoming a mini league baseball player will stun them if they see something resembling a baseball.
Once you've dispatched the elites young, remember to teabag them in front of their family for emotional trauma and psychological warfare.
Good luck, soldier.