I disagree with one of your stated assumptions and one of your implied assumptions. First, I certainly don't want to die before many of the beloved people around me (and I insist that I still love them quite a bit). However, I disagree with this stated assumption, because I disagree with your implicit assumption that when we should wish to die ought to be motivated mainly by a desire for self or others to avoid the sadness of grieving. It seems to me that we should be more motivated by a desire to avoid (and for others to avoid) the 'bad' of death. I would prefer not to die at all but since that doesn't seem to be an option, it seems wisest to accept the natural pattern of this world: to die after your beloved parents, before your children and grandchildren, and in roughly the same time span as siblings, friends, and spouses. It is also easier to accept mortality (your own and others) if you don't think this is the end, as many excellent philosophers such as Plato, Aquinas, Kant, and Kierkegaard...

I don't think the reality of the parent's serious illness and reduced lifespan in itself would make it morally wrong to reproduce. After all, there are plenty of children who grow up without ever meeting one of their parents or who lose one or both parents early in life that have a very fulfilling life on the whole. That being said I could imagine circumstances where I would encourage the parent not to reproduce. For example, if that family's specific circumstances would guarantee that the child would end up in utter poverty long-term after the parent's death. I don't think the 'potential harm of denying the other potential parent the chance to have a child' weighs too heavily in the decision. Clearly, you are either putting the future child in a circumstance that is likely to result in his/her overall flourishing or not. Your potential partner's harm of missing the chance to parent is a comparatively lesser matter since there are other ways that he/she might have the opportunity to flourish. ...

I think that the problem with that argument is that we can get nearly the same level of safety by sending the killer to jail for life. And given the imperfections of the justice system, there's a chance that we could execute an innocent person which is much worse than sending an innocent person to jail for a few years. Perhaps, if we were absolutely certain someone was guilty of murder and we had good reason to think that the death penalty had a significant deterrent value in preventing future murders it could be justified. But the deterrent value of the death penalty has been questioned in recent years.