My ds is only 9 months but is just eating what we eat so he usually eats bits off our plates when we go out. But some places like Monkey Nuts in crouch end do really nice childrens menus (like chargeilled chicken, mash and veg) it's usually too big but they're happy to wrap it up and he has it for lunch the next day
We perfected the 'smash and grab' lunch at that age. (Tea times/evenings far too stressful so we stuck to lunchtimes.) The idea is to get in and out as quickly as possible, the poster who mentioned you have a limited amount of time when they're happy to sit in the highchair is spot on.
I always took a bag of crayons/paper/stickers and the like, always had one course, dessert was pushing it! If the dc got restless we'd walk them round or take them outside to distract them.
It does get easier, they're 9 and 6 now and fantastic when eating out, we've even graduated to evenings