It seems to me that taking the fear any children might have about this sort of thing seriously, and not trying to discourage it, will end up leading to an adult whose risk assessment is rather poor. I certainly wouldn't tell my children, in so many words at least, to "get a grip", but I would try to explain why they have nothing to fear and should just enjoy the experience of thinking about it.
I do think that perhaps the school should have provided more information to the parents beforehand, but it sounds like the majority of the children were fascinated so I'd say the project would have been a success with better communication.