Agreed on children.

With immigration, I think the established residents will protest (with reason) that newcomers are coming to snatch benefits that they (the residents) paid for. Hurdles like citizenship could reduce the snatching, but many countries provide paths to citizenship for immigrants, and the U.S. offers birthright citizenship. I would prefer not to see immigration opponents have any more ammo. People are less likely to be concerned if the cash transfers are coming from a source outside the country; in that case the boosted economic activity is a win for everyone.

On the terminally-ill, of course you are right. Given medical costs, it's hard to imagine it would be profitable to keep someone on life support just to collect a basic income.

Your point on automation is interesting. Perhaps this points to a future in which automation (which sounds less farfetched than "robots") provides so many of our needs so cheaply that we will spend most of our time in leisure, pursuing hobbies and consuming entertainment. We have certainly been moving in that direction since the days of the washboard.