For me having children feels "closer to being a terminal value" than happiness does. So saying "you should have Children because it makes you happy" sounds like "You should have a meaningful job and a loving relationship with your wife because it decreases your chances of having a heart attack by 8%!" or "You should avoid murdering people because it looks bad on your resume".
I can believe that that's true for a significant portion of humanity- that they would choose to have children even knowing it would be bad for their happiness in the long run. It isn't true for me, though, and there are large numbers of people for whom it isn't (or else childlessness in the West wouldn't have risen so much).
There is a lot of research on this topic. I know later studies contradict earlier studies, but I'm not sure who to believe here. Wondering if anyone can help.
In case it isn't clear, the basic question is the effect of having children on happiness.