When COT aired, they hadn't mentioned Klingons and Trills not being able to reproduce yet, so I remember wondering they very same thing as the OP. After "Tears..." it became retroactively implied that since Worf and Jadzia can't have kids the old-fashioned way, their Gaian offspring must have been through some other genetic combination, even though we know they were married.
I definitely agree that there is no way in the world Worf becomes open-minded enough to just let Jadzia go off and do the deed with some other guy even if Bashir tells them its necessary to keep the gene pool varied. I'm guessing that Bashir would have come up with a way to do some artificial inseminations (which doesn't take much technology at all) without forcing people into physical couplings. And even then I imagine Worf putting up a fuss.