The implication of that question is that our little team of misfits will actually be able to change the world. Which... I didn't think this was that kind of game?
Dont' get me wrong, I don't disagree with pregnancy being end-game content, but that's because that's the logical end (you and your girls are reasonably dafe and stable, and it's time to think about a family - fin), rather than "we changed the world and now our children are safe".
Yes, I would totally have a child with Lin, right now, and entrust her (or him) to their half-brother or sister, for "safekeeping" once I'm gone. Along with Lin, really, since she is totally going to outlive the MC by several centuries.
No matter what, humans who are currently alive are not going to live more than a short century, so it's worth considering the very long term for our family, and that implies looking beyond the problems of the here and now.