A long awaited reunion

I need some advice. My sister is pregnant, we havent spoken to my father or his side of our family for about 10 years. I feel obligated to call my grandparents and let them know. But I cant bring myself to do it. I feel awkward just calling them after so long. I would love to finally speak to them, and I have a half sister that I''ve never even met. But the main thing is I hate my father. Hate is a strong word and that is why I use it. He is a loser, I honestly think he never loved me; and I know I dont love him. I guess I''m more afraid of my grandmother giving him my number or something. I cant tell her I dont want him having it, she just wouldnt understand. So how can I communicate with her and not my father? Its a very touchy subject with my family, thats why I''m asking you guys for some help...