Sorry to possibly burst everyone's bubble, but the tasks really aren't tasks. Whether you do the task or not makes no difference in the scheme of the ride. It will not affect the ride outcome in the slightest. During previews of the ride, my brothers and I purposely avoided doing the tasks and nothing changed with the ride experience.
That being said, I've heard many people say that it is incredibly important to keep your eyes on the screen and open at all times. I wasn't brave enough to look away.
Personally, I don't think I would take a five-year old on the ride. It's a little intense (well, it's a lot intense, really). That being said, I'm sure there are many people here that may disagree with me.
RyMickey