Christ even told his disciples to NOT stop the young children from coming to him! And as Peter reiterated, the promise is for us... AND OUR CHILDREN (Acts 2:39). Noah wasn't saved alone - his three sons... and their wives... were also saved. Lot's daughters were saved with him. Everyone in Rahab's house was saved... even the children. Where in the WORLD the WTBTS got that whole serving for many years FIRST thing... is beyond me! Well, the world, okay... But NO ONE served many years before being called/used, not even Moses. Sure, Moses spent many years in the wilderness... so as to get to know the terrain... but he wasn't serving while he was out there!
Regarding Noah: Let's remember the crowds of children, babies, pregnant women, teenagers, animals and men that were mercilessly drowned. If you are a young person, don't mistake this for a story of love and salvation. See it for what it is. A celebration of mass genocide.
Regarding Lot's Daughters: Remember that the Righteous man Lot offered his daughters to a sex crazed crowd of men to 'do with as they pleased.' Imagine your father doing that. But they were saved while all the children in S&G were slaughtered. Not a story of love and salvation if you're one of those children. But they watched their mother's life snuffed out, and something tells me that this righteous man was a pretty screwed up father, because his daughters responded to losing their home, friends, history and mother by getting him drunk and having sex with him. Well, it does sound messed up, but they really never had a chance. This was the father that offered them up to be raped by a crowd of men, so their views on sex were probably pretty screwed up
Regarding Rahab, the prostitute: Yep, she hung a cord, and her household was saved. They must have felt kind of bad about that as they listened the blood curdling screams of the children being slaughtered right outside their door. I don't suppose the children that were spared were ever the same after that. I have to wonder if they remembered it as a message of love and salvation.
So while you are young and your full life and options are laid out before you, ask some critical questions. You are young, so there are many things you may not know. Before you settle, check it all out. Sometimes just changing your point-of-view will shed a lot of light on any story. And before you distress too much about those children that were destoyed, consider that none of it ever even happened.