I don't think that the highly educated people who would join the expedition would at the same time be happy to se their colony die out, and would find it too on

I don't think that the highly educated people who would join the expedition would at the same time be happy to se their colony die out, and would find it too onerous to have children and pass their knowledge and fervor to the next generations. Again, I don't think that a self-sustained colony on another planet would be organized by Earth governments, and by people who are happy to live on Earth. I bet on projects like (the declared) Musk's Mars colony, and even more, on religious groups (remember Mayflower). It takes a lot of grit to leave the comforts of Earth and go live in highly inhospitable and limiting conditions of another world, for life. Do not compare it to traits of a typical middle-class college-educated coastal city dweller. Those are going to be very different people, with very different views on everything, including fertility and raising children.