A couple of options OP, but essentially yes, go to a family restaurant/ pub where you will hopefully stand a chance of avoiding people like Rosh.
I always took light finger food snacks like raisins and rice cakes for ds. They kept him occupied while not filling him up too much. I also took a bag of small toys with me and rotated them.
For a short period of time when ds was around 2 it just became too stressful and none of us enjoyed it, so we stopped going. He's almost 3 now and much better, though a real live wire who is incapable of sitting still for long so we tend to eat pretty fast or go to places where he can go off to a climbing frame or soft play area once he's eaten. We still try to avoid meals with my family (unless they're barbecues or buffets or whatever) when we know it will involve sitting down for 3 courses - that's still a bit beyond him! Unlike my niece who has sat quietly playing, drawing or colouring for as long as i can remember.
DH and i also used to take it in turns before our meals came out to take him for a little walk and show him around to keep him entertained. We then all ate together when the meals arrived.
And if we just wanted a break, we'd time eating so it co-incided with him sleeping - so maybe a late lunch for us, or an evening meal. We were extremely lucky that because DS is so active during the day he sleeps like a log at night. Up until he was 18 months we were able to do his bedtime routine, put his PJs on, lie him in his buggy wrapped in blankets and he either nodded off before we left the house or on the way to the pub/ restaurant. Of course this does rely on your chosen eatery being within walking distance and it not raining! He never, ever woke up and screamed and everyone commented how great it was.