Changing last names when getting married?

My bf just asked me to marry him and of course I said YES.

I have a son from a previous relationship who took his father’s last name which is Ryan Herman. My last name is Doughty.

Now my bf and I have a child together and the child took his last name which is Douglas and I will take that last name when I get married. So, when I do get married, can my son from the previous relation have the name Ryan Herman-Douglas? Like have two last names? Does his father have a say in this? I mean it’s not a huge deal but I’d like us to all have the same last name