When my daughter was little, or when we took our grandsons out, I always made sure that I carried a small "surprise" toy or book for each of them, and a small snack food. Then, if they became bored or restless, I would pull the "surprise" out of my bag and entertain them with it. They were just cheap toys or books (sometimes freebies that I got from fast food restaurants) but to the kids they were something "new" so they were interested.
When I was a kid, my parents always took us to full-service restaurants, never fast food. Two reasons: 1. there weren't any fast food restaurants back then, and 2. my dad always wanted
service. He didn't even like to go to buffets or salad bars. (If the restaurant had a salad bar included with the dinner, my dad insisted that the waiter get the salad for him!) Anyway, my brother and I learned real quick how to behave in a formal restaurant. It was no big deal. We knew how to use our napkins properly, which utensils to use, how to open a lobster, what a Roquefort dressing was, etc.
I was a teenager the first time I went to a McDonald's!
Kids need to learn the difference between fast food kid places and fine dining. Fast food places are for play and noise; fine dining is for sitting and polite conversation. Yes, conversation. I don't believe children should be taken to a nice restaurant and be told to just shut up and sit still. They should be included in intelligent adult conversation. That is how they learn to behave in a civilized way.