We booked a row across on the 777-200 (1-2-1). when we boarded I just put my kids in the middle and we sat on the aisles. Nobody said a word, and they certainly "knew" that we weren't in our assigned seats since my son had a kids meal. I also wonder if the point is they don't want your loud kid sitting next to somebody else in the middle section, so if both your kids are there they really don't care? No idea.

But anyway, on the reverse herringbone seats on AF the two middle seats aren't actually "that" close to each other. My kids could lean over and talk to each other but couldn't play switch together, for example. If anything it's easier to communicate with the person across the aisle, your heads are actually closer and you can see each other.