My father's life was saved by a kidney transplant. He recevied his from a sibling. That being said, in the situation you describe, I'd have gone with no. I'm a pretty soft hearted person and a care-giver by nature, but to my mind, in the same circumstances, my first duty would be to myself and my grandson (I don't have a grandson, I'm saying if I were in your shoes). Or at least I think that's how I'd go. There's really no right and wrong in the situation. There's only what you can live with.

PS: I'm sorry for your loss.