honestly? it varies, with the same DC, too many factors. (are they tired, do they want to go, is something amaznig being served on the menu that they wouldn't normally get at home)
we have had situations where 1 week with a 2 year old we got an extra scoop of ice cream for free as DC had been "amazing, little angels, a dream for serving staff"... lots of big eye coos coming from tables next door, quiet, respectful, only 1 bathroom trip. you'd think we had this every time to look at us.
next week? slightly tired with a "boring" (what you get at home menu) shit show involving DH and I tag teaming, about 7 trips to the bathroom, food being thrown on the floor, about 5 knives and forks on the floor.. fucking nightmare... we ended up just asking for take home boxes for the food amidst a flurry of "fuck this, let's try again in 6 months"...
if you saw us at the first restaurant you'd think we had it cracked. we haven't!!!! just luck. i often think back to that period/age group when we're out eating - it couldn't possibly be more embarassing and worse than that 2nd attempt eating out!
3+ is a safer bet but still open to wild vairance, IMHO.