I have not seen the specific comment by Jan Leeming, but it is something that tends to be quite british in style. Having lived abroad and taken a child from the age of 2 to Syria , and other countries, I found that the two way level of acceptance far better than in Britian. While he was young, if we went to a restaurant I would choose a table which I could sort of block him in, so that he needed to pass me to get to other tables. But that was the only thing I needed to do. I always carried small notebooks , little games etc ., to keep him occupied if he had finished his food and needed to stay there. So that was my side of the "bargain"
On the other hand, I was able to get firstly , when he was very little, a plate so that I could give hims something from my choice. Once he was a little older he was offered a half portion of anything that was on the menu, which did NOT include chicken nuggets or fish fingers. He was treated politely and was part of the party, not someone fed the same boring - and not very healthy - food and expected to sit for a long time while the adults sat and drank or whatever.
On the continent I found cafes and restaurants expected to have the whole family and were relaxed about it. There were many times that the owners or the staff offered to take him and play with him, whilst we had coffee. The atmosphere was welcoming and relaxed, no feeling that I had to apologise for even having my child with me, however well behaved he was.
That atmosphere meant that he grew up understanding the way to behave , and he learnt many things about all sorts of food and drink.
How much you paid for the food you ate did not dictate who was able to be there. There have been many loud and rowdy people at tables close to ours, whose manners were far worse than at our table I can assure you. My son now has a son of his own who is taken to any restaurant or cafe , they choose. Feeling that this is normal and natural is part of growing up and learning how to be in public. But I do accept it can be very difficult for owners and staff to work out how to deal with badly behaved customers.
I accept that in several places I know, there are certain families who staff are told to tell them that they are full and have no vacancies , and it is understandable when those particular people not only caused problems but lost them other clients too. You cant blame them as there seems little other options open to owners .
So whilst I can understand an individual getting upset or annoyed by what they have planned to be a special occasion, not turning out to be what they wanted; they do need to remember that they did not book the complete restaurant for themselves , and whilst they could expect reasonable behaviour from other people, if you want something to be just as you want it, then you need to plan for this special occasion to be in your control, so having someone come in and cook for you, or make less assumptions as to how other people will act. I do think that these days people seem to think that they are entitled to do just what they want, without regard to others, and are more selfish than in the past.
Personally I was brought up to the old adage of do as you would be done by, not grab what you can and go hang to the rest . But I do put part of that down to the Thatcher reign where she taught people to put self first, but that is just my own thoughts.