Sometimes, when I receive the daily report, my son informs me that they played at the home of a child I don't know. In most cases, the caretakers know each other from home, the playground, or mutual friends, and make the arrangements to introduce the kids. Having worked for us for almost five years, I trust my nanny's judgment and know she wouldn't take my kids to an unsafe environment, but it is a bit odd to know that my kids are visiting a place I've never been.
When I mentioned the unusual situation to a fellow working mom, she told me that she never allows her kids to play at homes where she doesn't know the parents. In those situations, she requires the new friends to come to her. Every parent has their own set of rules, but would you allow your kids to play in unfamiliar homes?