Well I didn't really HAVE a problem until you jumped on me. I was just half joking when I mentioned that the sign looks like it was written by a child.
However since you want to create a problem then yes - AS I MENTIONED I have a problem with the way the sign is printed. It's a professional event and if you want to communicate to people that they cannot bring their children in, then at show them the courtesy of printing a nice sign with proper grammar. What does it take, all of FIVE minutes in the office to do this.
I am sure that such a sign makes a WONDERFUL impression on journalists coming to review the event, not for it's content but for the irony displayed.
And yes, I have a problem with the message. I have been to the Open many times and have never seen a problem with children there. Since this is an event that many people travel a great distance to I think that the attendees deserve some prior warning that their young children would not be welcome. I am not a big fan of last minute ad-hoc rule changes.
Do I have a problem with authority? What kind of silly question is that? Yes I am just rebellious for rebellion's sake. Do you have a problem with courtesy?