Hello, James.
First, it would be irresponsible of me not to ask if your grandfather is being treated or is on any kind of medication for his depression. Is he? Meditation is not a cure for depression, especially for a person who has voiced suicidal thoughts.
So... for now I'm going to assume he has seen doctors and is being treated for his issues. That said, here are a few books on meditation, for beginners:
Zen Mind, Beginner's MindHow to Meditate
Buddhism Plain and Simple