J.F.
I kind of went through this but I have a daughter. In the end I decided that regardless of the father and who or what he may be and whether there would ever been a relationship between her and him, I kept her last name to match his (he is her father) and she will marry someday and it will change anyway. I have just never made a big deal about her name and my name being different and she does not seem to care.
I believe that IN law says that the father has a say in the last name regardless of his involvement with the child.