I'm going to cut off my father before the birth of his first grandchild
What did your father do to deserve this from you?
We do not get along at all and I know this would hurt him.
Your father would be devastated if you cut him out of your life and his grandchild's life. Family is important, so you should try to make up with your father so that there is no resentment between you.
Let's just say we had a fallout.
Sometimes families do have fallouts. But that does not mean you can't reconnect with him. The birth of a child is something that everyone looks forward to, maybe this can bring you both closer to each other again.