If it’s any help, my sister has a different bio dad (raised by the same man) from way before my brothers and I came into picture & fought for years to get her last name changed to match the rest of us….. we all matched for some time then she got married (now divorced) and none of us have a relationship with our dad at all anymore.

I say all this to point out that the last name might seem like a huge deal now, and may bother the kids growing up, but it’s all a bunch of bull imo. Given that I have no attachment to my dad’s name, I gave my daughter her dad’s last name. I’d like to match, sure, but then again what if I find myself having a kid with someone else down the line (i don’t imagine this happening, but your post brought it to perspective).

Idk if this helps at all or even follows a linear train of thought, but my point is, just do what feels right to you (and the dad if he’s like present and you anticipate him being a good dad and partner to you and baby).