One thing that doesn't seem to be entered into people's conversations about the value of having kids is value of information.
There a common thought that Effective Altruists can, through careful, good parenting, impart positive values and competence to their descendants. However, it is highly uncertain how well this will actually go. And given the large differences in cost-effectiveness from top causes to secondary ones, and from Effective Altruism to other social movements, it is pretty important to know how likely our kids are to remain faithful to Effective Altruist principles. Yes there is existing evidence on parent-child transmission of other social movements and religions, but who knows how well it will generalize.
Answering this question within 2-3 decades would provide significant value to future Effective Altruists about whether they should have kids.
Of course, the importance of this consideration depends greatly on the expected size of the EA movement in the future.
Maybe this could be a small discussion within EA, but I'd worry people will be or will feel judged on whether or not they have kids, and that would make EA very unwelcoming. There's also the question of how demanding EA should be in the first place.
Even if my own (weak, uncertain) position turned out to be better, I wouldn't want people to feel judged for acting against it.
Are you talking about the general conversations about whether EAs should have kids, or are you talking about the point I'm making right here?
Either way, I'm confident we are all perfectly capable of discussing right and wrong action on such issues while steering clear of moralistic judging, just as we have generally done on other issues such as diet and donations.