@Lyanhyrt
When is there going to be another set of children?
Actually might not be possible, depending on what de-aging magic happened.
But, AFAIK, women are born with a set amount of eggs and when you go through puberty, well, you know the rest. But these eggs also start dying off fairly rapidly (going from over a million gametes when you're a newborn to ~300,000 when you go through puberty). And it continues from there. And, of course, women lose them when they aren't fertilized. So over the course of puberty to menopause women have like 200-500 viable eggs. And they get worse in quality over time, as well.
So chances are oven works fine but we're just no longer cooking with gas. Whereas grandpa... well, men don't stop producing new sperm so even the oldest guy still alive could theoretically impregnate a woman just fine. Which considering they've already had kids and are getting a second chance at being young again it's just more reason to go at it as much as they want if this is the case.