I have my mother's maiden name.
Personally, I like it that way. LOL.
But, in your situation if he is going on the Birth Certificate, I doubt the last name of the child would count for much. If he is going into this WANTING to be a father, then I would consider using his last name.... If you are kinda dragging him a bit, I'd prob just go with yours.
I think people are getting very much past the whole last name things with all the non-traditional families out there. So I say in the end, just pick the name you like best and want the kid to have.