The last thing I'll be doing in my retirement is providing regular childcare. I'll offer to always help out in emergencies and maybe a week in the summer holidays, or for a night out. But not all-day childcare several days a week.
Tbh you hear the same cliches trotted out often:
my parents love to have all of my children 9-5 every day.
They'd be horrified if we didn't let them mind them.
They offered; no they insisted.
They're so thrilled they get to see their dgc every day.
I offered money and they refused and insisted they do it for free.
They know that I'd be happy to find an alternative if they want me to.
People are kidding themselves. I know several grandparents who provide childcare. Yes they love their dgc and dc. Yes they want to help. But as years pass and more dc often arrive, they find themselves stuck, obligated, not wanting to offend or upset their dc...unable to stop arrangements that have been in place months or years when they know the financial impact on their dc would be huge...that the care is 100% relied upon or their dc will suffer.
I have never, ever, experienced anyone who has free childcare from family but also saves the amount they would have had to spend in cc. They often can't, because they need it. Which makes the family childcare necessary to them, and eventually, expected.
In most cases it's hugely selfish of people imo.