When the world was destroyed , God said that the thoughts of man were continually wicked .....but He did not tell Noah to build a dingy to pull behind for the "innocent , unaccountability children. " . The children were as guilty of the evil thoughts as the adults...and so they were also destroyed.
Same thing in Sodom ..God was asked to spare the city if there were just 10 righteous in that thriving city of men , women , children and infants ...and not 10 were found. They were all destroyed because they were evil in the Holy eyes of God. There is no free pass for infants , children , the retarded etc . All men everywhere are saved only by the Grace of God..NEVER on their own merits