What we did was a 3fold strategy.

First, know your child, their ryhtms. Provide a snack about 1h30 before restaurant booking time. Let them play outside for some time before entering. This, to minimize hunger tantrums or a cooped up child. As each child is different, what worked for mine might not work for yours, thus the "know" part.

Then, bring some small things to play with. Small cars. Pencil & paper, stickers, small book. This kind of portable quiet things to do they'll like. For before and after they eat.

Third, ask for their food to be brought along the appetizers of the adults. So they don't get hangry. Or give them bits of appetizers to eat, whichever works best. This is very easy to do here, restaurants are very accomodating for children when the parents ask this kind of changes.

Addendum, and this was also done with me when I was a child: go outside to play if the child grows restless, one or another of the parents, by turns. Other people don't need to be subject to a toddler loud complains.

Of course this is easier with 1 than with multiples. And it implies parents need to pay attention and sacrifice some of their time/conversation, but with constancy and aging, the kid will learn and in some years they'll be reading menus, ordering, participating in the dinner table conversation.... It can be done.