For us, once we allow them to do the electronic thing at restaurants once, they want it every time. So we've had to go cold turkey on them in public... once they got that message they made the most of the situation.
Having said that, we do usually take something for them to do (but ours are 8, 6 and 4 - so slightly younger age group) - partly because we want to have adult conversation without them trying to understand it all, eg. talking about travelling they don't know where places are, cities and sights etc.
Our latest "restaurant activity" is a thing called Rory's story cubes, 9 dice with pictures on them... you roll them and have to make a story from the pictures that come up (tree, lightening, alien, hands, compass etc). Quite a challenge for kids and adults, almost like charades without the need to stand up in the middle of the room, LOL.
Ours can have 3 dice each and make up their own stories, or we have all 9 and take turns. For extreme story telling you keep rolling the dice to keep the story going (which gets very wacky).
So yes, YANBU and they need to learn the basic art of conversation and behaviour, but you also need to be realistic about their attention span/interest in adult conversation and have a plan for their entertainment (either electronic or something else).
"Back in my day" I do recall reading books in restaurants, so I guess that is as unsociable as electronic.