The people who complained to elders about distracting youngsters were, in my congregation, primarily females who had been mothers. There was one black sister in her late 60s who'd brought up five children. She was the first to give the annoyed look when a disturbance lasted a long time. She was also very complimentary of parents who were diligent about such things.
There was also a middle-aged German sister who'd get peeved. Sometimes she'd march over to the parent with her arms out, almost ordering them to hand over the child. (Whoa!) Much of the time, though, she'd glare at the elders and point in their direction.
Sometimes it was young mothers who tried to keep their kids in line--and who seemed to resent it when others didn't. They wouldn't usually walk up to an elder's chair during the meeting, but they would sometimes wait in the back for one to walk by--or bring it up some other time when they wouldn't be found as the complainer.
By the way, I just wanted to mention that, to me, children were not my pet peeve when it came to disturbances. I was completely annoyed by adults who would speak out loud. There was one elder on the body who used to do this. Whenever he'd speak to his wife--or to anyone else--he'd just say it out loud as if no meeting was even going on. Eventually I asked him if he knew how loud he was during the meetings. I swear, whenever he'd talk, the entire congregation would turn in his direction as if to say, "WTF??!"
I can think of at least five or six adults over the years who were completely whisper challenged.