Name change mid pregnancy

My boyfriend chose the first name for our girl and I was like "eh whatever it's your first kid, have at it." Well he just left me and my other 2 kids high and dry over the weekend.. So I think I'm going to name her what I had in mind.... Is that wrong? I mean the baby will still have his last name.. Only cause my kids and I have my married name (been divorced for years) and I feel weird giving a baby with another man my ex husbands last name.