I don't owe having children to your children, or to you.
You can have children if you want, but I'm not requiring that of you.
If your children take care of me late in life, it's because they're exchanging their work for money. And the reason they're obligated to exchange their work for money is because that's the economic system into which their parents decided to bring them.
You do not owe anything to anyone here. You just cannot construct a moral high ground based on your childlessness.
It is not moral to not have children. Paraphrasing Kant: An action is moral, if the state improves when everyone does it.
You cannot recommend everyone to not have children, since you depend on them. So why bring it up as an argument in a thread about climate change in the first place?
The argument is hypocritical. It just does not make much sense.
Do you see it as an optimization problem, where others have exactly enough children to care for you at old age, but so few that the climate suffers as little as possible? If so, you are still relying on the children and do not gain any more imaginary rights to pollute than those parents.
You can have children if you want, but I'm not requiring that of you.
If your children take care of me late in life, it's because they're exchanging their work for money. And the reason they're obligated to exchange their work for money is because that's the economic system into which their parents decided to bring them.