Now you're arguing semantics. Individuals can be replaced. They cannot be remade, they cannot be recreated as you're arguing would be done. They simply are disposable. children die every day, society moves on. When you get a job, and you're fired and someone else is hired in your place, you're replaced. Replacements are possible for children. I'm taking the cruel unfeeling standpoint and saying more children can be made. They would be different but as children are not functioning members of society until they become self productive, and are merely investments until then, replacing them would be as simple as having more kids. But I do see where you're coming from. When it comes to the laughs, the love, the individuality, there will be very few who will ever be the same in an even slightly similar way. But lets not get silly here, there are many look alikes of every person. I met my doppleganger a few times just a few states over. But none the less, he is not me. Then I've met my mental clone and became short-lived friends with them. It's not fun talking to people who have nothing new to say. It's interesting the first week but then they become dead to you. But anyway, what holds true is children are investements and hold nothing but sentimental value to society until they are productive adults, thus having humanity continue on after the children vanished would be as simple as having more children. In that sense, the purpose they serve is to continue on humanity's endeavors, and by that means, they are replaceable in the jobs they hold. Not as individuals. by that point you are correct. But I also hold my own facts in hand. I doubt you're ignorant enough to disagree with ALL of the hard points I'm making.
Generally, I'm open minded. But with that, I have to be a bit of a bastard and say shit nobody wants to hear. One of them is, children are replaceable.