When passengers suddenly get quiet, it is almost never a good sign. In this case Chuck lucked out but in general my experience has shown it means that they are getting sick. I have been flying for way over half of my life and over time it seems you develop a second sense about these things. I can often just look at a passenger and will know if he/she is a puker or not. And it is usually the ones who are way too excited when they show up and talk way too much. It shows that they are nervous even though they don’t even know it yet. I have surprised a few when I gave them an extra bag because they thought for sure they could handle the mission but were glad later on that I prepared them.
What seems to be the worst part (I know from watching since I don’t get sick myself) is that once you get sick in a helicopter (or plane for that matter), it will take you a long time before you recover from it long after landing.

Kids are more tricky. I usually did better not ever bringing up that there is a possibility of getting sick. That way they don’t think about it, have no idea they COULD get sick, and just enjoy the awesome ride while you keep them engaged. It almost always works. But if you mention it they start thinking about it. They get scared “Wait? I can get sick?”, and you almost guaranteed have a puker who, which makes kids worse than adults, NEVER give you a heads up 😉