I would agree with all that you said. I can think of many other persons whose lives have gone wrong in big ways, and it is good to see that all of these children found some amount of happiness and balance, despite the curve balls one encounters in life.
One other point: even though a few of the adults expressed displeasure at having their lives under a microscope every 7 years, I think overall it is a good thing for them each in a way. Most people could not tell you what their goals had been when they were 7, not all of them anyway. But the mere fact that each of the people in this film knows that their goals and progress will be re-visited again in a few years, keeps those goals fresh in their minds. If they change their goals, that is fine. But they will consciously change them, since they know they will be asked about them again for the film. And that is good. It is like having a buddy system in a way. Life passes by so quickly. These 7 year meetings probably help these people check and re-check themselves, for what they feel is important in their own lives. As much as an imposition it must be for them, it does have that benefit, I think.