When I was about ten years old, a Bethelite told me how one of the Governing Body answered that question at morning worship.
The GB member said, "Folks will ask you, 'But what about all the babies and children at Armageddon? How can Jehovah kill them?' Well, little rats grow up into big rats!"
The Bethelite told me this story with a big smile across his face, entirely satisfied with this answer.
It disturbed the hell out of me.