Well, this thread has gotten crazy!
We just got back from 8 days at WDW with a 7 year old and a 5 year old, and they did pretty well. We only took nap breaks on the first 2 days, I think because we were tired from traveling, but we were OK after that. We took long breaks for lunches and occasionally just sat on a bench for a few minutes to regroup. I noticed the little guy would start to whine before meals and would perk up significantly after his lunch hit his stomach. We slept in later than I would have on my own, but crowds were not too bad so it was not imperative to be at the parks at opening, and the weather was bearable, which made a difference, I think. Our only meltdown was when the 7 year old demanded to go to the pool when the rest of us wanted to go to bed. She was exhausted and had been asking patiently for 3 days, so I decided to give her a break. She got 10 minutes in the pool and went to bed happy afterward. The little one demanded to go on Spaceship Earth but agreed that we would go later when we looked at the long line and explained we would go later when the line died down.
As for the rest of this thread, I think as usual, it's hard to judge others when you don't know the whole story. Everyone has bad days - kids and parents, and sometimes both. One episode you witness at WDW or the mall may not be indicative of how their days usually go. Little kids sometimes can't tell you what sets them off. Sometimes adults can't tell you what sets them off. Just about anything can be the straw the broke the camel's back when you are tired or hungry or hot or all of the above. Every parent and child are different and the way they interact is unique, and may change as the kids grow. This requires constant adjustments on both ends. Add several kids with different temperaments and it only adds to the challenge. I've seen kids sit quietly at the table at restaurants, but mine never did. Some kids just have easy going temperaments, I guess. I certainly don't get up and run around the table and talk loudly and cry and whine at meal times, but my kids have done it. They didn't learn it from me. They were just over stimulated by the environment. It happens. I'm confident that they will grow up to be adults who sit quietly at mealtimes.