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.