I wonder, while Cullen is attracted to Elves, how would he feel about having an Elf-blooded child?
While we know that a lot of humans take elven lovers, it does seems like something that's considered an embarrassment, at least when it comes to nobility? I don't think Cullen wouldn't accept an Elf-blooded child, but how do you think he'd deal with the social stigma, even if it's mother was the Inquisitor?
The stigma wouldn't be so much on the child (as they'd look human and could easily pass as one if no one told otherwise), but on the involvement between the human and the elf, specially if it's a commited relationship. Soris from DAO, in example, has a human lover, but it only goes awry for them when he marries her.
I feel like Cullen would have cared more about such a thing if this was a couple years ago, when he was Knight-Captain and had a reputation to maintain, the face of the Order to save. We don't know much about current Cullen, but everything leads to a Cullen who's sort of drifting along, neither here nor there, finding his place in the world. But he seems like he's come to a point of his life where he just doesn't care anymore - what people will say if he bangs the boss, what people will say if he bangs the elven boss, what if babies happen. He knows who he is, at least, and doesn't need anybody to tell him what he should be. So at this point? I don't think Cullen would give a rat's ass. If he loves Lavellan and their love produces a little elf-blooded Noodlet, he'll be the happiest father ever, and anyone who has an opinion can shove it.
Plus, you know, it's the Inquisitor. Even if there was any concern over social stigmas left, he's having a child with the Herald of Andraste herself (nevermind that she may despise that name, for all purposes that's what Andrastians are gonna call her like it or not). Andraste's chosen has chosen him. Put a stigma on that. 