Yes, retired vigorous women (carefully vetted) are an untapped resource for a Granny Brigade.

You are good at this mommy thing. But some people might not have a natural talent at first and might be more willing to have children in the first place if they knew there was a functioning Granny Brigade. Such a Brigade could also run some of those other functions. Even simple, professional Early Childhood classes. People get DEGREES in Early Childhood. Such a professional could be paid to give a talk a few times a year. It might give courage to give birth at all.

Running around to garage sales in the hopes that some of the stuff might pertain to infancy needs is one thing. But a centralized source for used Kid Stuff is a lot more focused. A garage sale or thrift shop can have tons of stuff irrelevant to infant care or children's clothing.

So while you are not the granny, you might be the one to pull the grannies together.

These days women who have no grandchildren are a dime a dozen. Including those that never had children at all.

Naturally they would have to be carefully vetted.

Maybe men would find a New Dad Beer Night useful.