That's a great story with a great ending. I've been in similar situations with similar outcomes. I've been in other similar situations with parents casting a scornful eye at me and scolding their children for talking to strangers. (And you can't blame a parent for teaching their children not to talk to strangers in today's world.) Bottom line is, there are all kinds of people in this world. You do your best and hope for the best and most times it works out for the best. But there are no guarantees and sometimes it doesn't turn out right.
Take time to smell the roses and love the grandkids.