Oh. That's so sad. But at least your father-in-law knew that your wife was pregnant and would have a beautiful kid. But for you and and yours, I hope you find strength to move past this.
My sympathies to you. My wife lost her mother in a drowning accident in the home when she was 7 months pregnant with our first child. I can only tell you that the joy of the arrival of your new child will help her but not completely. Your wife will probably suffer from a lot of (completely irrational) guilt about the loss of her father on top of normal post-partum depression so be prepared for that. Don't know if it would help, but here's a photo of us with our little one so that you can see that things do get better: