These etiquette experts say that new approaches are needed because parents no longer have the stomach, time or know-how to play bad cop and teach manners. Dinnertime has become a free-for-all in many households, with packed family schedules, the television on in the background and a modern-day belief of many parents that they should simply let children be children.

Some of these manners-minders acknowledge that they can sound like curmudgeons, just another generation of older folks mourning the lost habits of more refined times. But they also say that parents welcome their efforts as a way of outsourcing the hard work of teaching youngsters to follow rules.

During a recent family night at Chenery Park, Joseph Kowal, an owner, roamed among the regulars and newcomers, saying hello and occasionally playing parental ally. He’s got a twinkle in his eye but a steely commitment to having children — even if they’re not etiquette role models — at least sit politely and not scream or throw food.

“Some parents will say, ‘Uncle Joe’s going to come up here, and he’s going to be cross with you,’ ” Mr. Kowal said. “They use that to their advantage.” He recalled one child who wouldn’t settle down, and he threatened to tape the child’s mouth. The child told him to go ahead and try.

“I went to my office, got some blue painter’s tape, came back and ripped a piece off,” he said. The kid piped down. “The parents looked at me like, ‘We’re going to try that at home.’ ”