IMO all discussion of the population crisis needs to begin as a simple statement of fact of a public good problem: having kids is needed to perpetuate humanity (public good); and however rewarding, it's hard work (private cost).
Not with calling out the childless, or extolling the joys of parenthood, or saying that "a real man has a family" or any of that. Not with criticism, not with solutions.
Let's just soberly include this on the list of important public good problems - not an existential risk for the species, but a severe and immediate existential risk for our most load-bearing institutions, starting with almost all developed world social democracies. And go from there.
With that start, my mechanism designer mind jumps to taxes and subsidies, which I think is far more useful than going to creative new ways to brand the epic glory of handling feces or guilt trip DINKs or....
(I do literally with zero irony think handling feces for the purpose of furthering the human race is epic and glorious, but I chose to cultivate that aesthetic, and if I hadn't there is no carnivore aurelius meme that would have sold me on it.)