It would be cruel to their children.
The whole "cruel to children" aspect is flawed. It only self-identifies individuals with a world view that is very earth-centric. We need a societal system where such a position is seen as an honorable one. That's why I liked the Antarctica bit of the submission. We ALL need to learn and change.
Having said that I worry about the sustainability of these projects. If these are not indefinitely sustainable on arrival, then future generations are doomed to die out with no hope of survival. I’ve no problem with a carefully judged risk, there are no guarantees in life, but there has to at least be a reasonable chance.