I don’t have a problem with the restaurant doing this, but is seems like a money loser, unless the primary clients of the restaurant are grumpy, old people. I would think they would lose a lot more business from families with young children then they will gain.
I like the idea of putting up signs saying that unruly children will be asked to leave, but the arbitrary, 6 year old limit seems a bit silly. It’s not like loud, bratty, 5 year olds, (with parents who tolerate that behavior), suddenly become polite and quiet on their 6th birthdays.
Most households in this country no longer have children under 18 living in them so this is a very good idea to attract the crowds who would like to enjoy their dinners out.