I think parents need to know their particular children and what they're like.
I have very, very clear memories of when I was little, and I know that my parents were careful of the situations they took me into, when I was little. Fancy restaurants and places where there was a long wait were generally out because I was NOT a patient child. But if the wait got to be too long and I DID get antsy, I remember many times when my dad would carry me outside to give me a change of scene for a bit. Roaming around the restaurant itself was NOT an option, and frankly, did not even pop into my head to do. Outside with Dad was the only alternative.
Now, when I got a little older (say, 4 years old and on), I was very easily entertained by just giving me a paper napkin or placemat, and a pen, and I'd draw. (Or better yet--those restaurants where the WHOLE "tablecloth" is paper.

) And there was even an age range where my parents allowed me to read books in the restaurant, especially if there was going to be a long wait. Of course, once I reached an appropriate age, the expectation was to participate in conversation with the family and be patient no matter what happened. But the whole point of all of that was that I was not allowed to be loud or disruptive or obnoxious to other restaurant patrons--and I'm sure people would rather a little kid be there quietly with her nose in a book than doing all the stuff you guys have mentioned.
Things I was also NOT allowed to do was make a mess or be rude to the wait staff. I remember getting a lot of compliments from waiters and waitresses because I did NOT act up in the restaurant like a lot of other kids my age. I also remember I used to really surprise them because starting at about 3 years old, I would order my own food instead of my parents ordering for me. "Please" and "thank you" were things I learned VERY early. (This was another advantage to learning to read early--I could actually look at the menu and have a part in making a decision even at 3.) And if the food was going to be messy, my parents helped me when I was really little instead of letting me make a mess.
And they told me, too, when I was a baby/toddler, they would PICK UP after the inevitable mess kids that age make when they are too young to know any better, rather than make the wait staff do that. Now THAT is something that pisses me off about children in restaurants--when parents do not clean up the mess their children make, because frankly, a little kid's mess is above and beyond what the wait staff should have to deal with by themselves.