Being a single parent now and not giving baby no.2 he’s last name

So I unexpectedly got pregnant again our relationship has been rocky but we finally decided to split 1 day before I found out I was pregnant. He has been irresponsible with his daughter while only sending $50-$100 weekly i now have to get a 2nd job to provide for my children. My daughter has not seen him whatsoever and he just randomly disappears for weeks I don’t think that’s healthy for my children and I don’t want him involved if he does it just because he feel he has to not because he wants to. Am I being selfish for him not being present at birth and the baby having his last name ?