It has been completely filmed. They had to do it all beforehand to avoid being shut down by Lord of the Flies comparisons.
Unfortunately, I am not aloud to know anything, because if CBS finds out about any of the participants releasing information they're not supposed to, there are serious consequences, which I'm not even sure I'm supposed to mention.
What I can tell you is that I wouldn't worry about it being TOO "feel good." There certainly will be angry, intense moments. Not Lord of the Flies intense, but intense.
As far as the success of the show goes, my number one concern would be whether or not adults have any particular interest in watching a television show in which all of the contestants are kids, especially if they cry a lot. Which they do.