There were a couple of things that made me uneasy, mainly that they did seem to be a bit unprepared/negligent on a couple of things.
One of the first things the guy said was that they had never sailed the boat in heavy seas and didn't know how it would handle. So sailing around the world in it with two kids didn't seem like a particularly wise thing to do until you had fully stretched the capabilities of the boat and had a comfortable handle on what it could and couldn't do.
Then the fish thing was just irresponsible. They looked it up on the internet AFTER they ate it, when they were already ill. Why not before?
Apart from that, I do think it was fairly selfish of them, in that the kids were too young to get much benefit out of it. Yes they would see the world, but at that age would only remember living for a year on a white plastic boat and swimming in the sea. It's not like they would really understand anything about where they had been and what they had seen.
Having said that, there are other benefits. The kids have learned how to entertain themselves without TV/Nintendo or spending money etc. which is a life skill in itself, and they have obviously bonded as a family. They would have got more out of it had they been a couple of years older though.
On the whole I agree with MrsC2010 in that sailing isn't an extreme sport and done responsibly can be extremely safe. However, there were a couple of things that I felt were irresponsible, and I definitely think the parents were doing it more for their own amusement than for anything the kids might get out of it. Not that this is necessarily a problem. Maybe the kids have also learnt that they are not the only ones in the world and don't get to dictate what adults do or don't get to do, let alone what the family is going to eat for dinner etc.
D