I appreciate where your coming from, and I have two kids one 12 and another 6.
I've often been in places with kids screaming the walls down and it's bloody annoying. But ours from an early age have been taken them out to eat and to coffee shops. We made it clear from the start that they sit still and be quiet and they do. I even had a colleague once on hearing we were taking them out comment on how brave we were and he wouldn't take his kids out. He and his wife were very well off and thought they were the dogs danglies with their money, flash cars, golf club membership etc etc. But their kids were horrors.
This afternoon we went to the cinema, the place was full of kids all making a racket and the nosiest one of all was the mum giving her kids running commentary on what was happening, not even lowering her voice. My six year old sat there not a whisper. Same on long haul flights, where I've had two people one out going and another one on the incoming flight tap me on the shoulder and say how well behaved they were.
It's all I how you bring them up and solely down to the parents. I feel my kids shouldn't have an impact on others and their enjoyment of a meal, coffee or flight, etc. My kids are far from perfect but they know when to behave.