One day, when I was visiting my aunt, she was putting some fragile items (she normally kept on coffee tables and low shelves) away. I asked her why and she told me someone with a bratty kid was coming over. "I resnt it," she told me. "My three kids know not to touch anything that doesn't belong to them, but I have to pick things up because so-and-so is coming over." It's true. Her kids were always very well-mannered. As a result, her middle child (the only one with kids so far) is also raising 2 very well-behaved kids.
It was probably easier (and cheaper) for her to put the stuff away, than to say something, though my aunt isn't afraid to tell it like it is.