Stop while ahead IMO.
I'll expand on my "wow" post. I would ask you this: why would you assume that this family shares your "values" (such as they may be) and attitude toward such children? For that matter, why should they care whether you think they should have more kids? And what business is it of yours?
Just common sense.
Nothing wrong with using the brains God gave you.
I'm not talking medical secrets here, most women know about risks of having children late in life.