Experiencing a second childhood through other people is wrong and objectifying. It is treating people as means to the ends of others. Children are people in their own right, not receptacles for solving their parents’ mental problems.
It is unethical to attempt ‘self-repair’ through someone else, especially when there is a real possibility of ‘breaking’ someone else.
And precisely those who had a difficult childhood should understand that this is an option and should want to prevent this option from someone else.
You can try to ‘repair’ in other ways, for example by adopting existing children. Even if it will not be a correction of your childhood, since there is really no possibility of correction by proxy (a good childhood for your children will not retroactively change yours), it will at least be a correction for children born without parents, or without parents who can or want to care of them. So even if it is not a psychological correction, it will be a social and moral correction.
Even if you do your best to give your children a wonderful childhood, the option of preventing your children from having a difficult childhood is beyond your control. Serious and devastating harm may come from anywhere, at any time, and without any possibility of anticipating it in advance and being accordingly prepared for it. Life is so fragile, and people are so vulnerable. Of all people, those who had a difficult childhood should know this.