so, would it be weird to give my baby my ex boyfriends last name?

Alright, am pregnant, no longer with the father... But I was still planning on giving the baby his last name. He has no issue with this at all and it just seems strange to me to give it my last name because our two year old has his last name already. Some people say I should give it my last name instead, since I am the one doing everything... But it seems strange for my kids to both have two different last names, does that make sense? Opinion will be appreciated, please and thank you.