My father did not want to hear about hospice either, as he, too, equated it with 'giving up'. When he reached the point that your son has reached, the Dr had someone from hospice visit with him everyday at the hospital. At first, he was very resistant, but the hospice nurse was trained in dealing with this very issue. In short order, he warmed up to the idea, due in large part, I beleive to the hospice nurse's approach and attitude. My father and our entire family were treated with the utmost respect, care, empathy and warmth by the hospice staff. It was perhaps the best, most comprehensive care he'd experieneced the whole journey: physically, emotionally and spiritually.
Hospice is not 'giving up', it is merely shifting goals. I believe that hospice staff can enable your son, daughter in law and the rest of your family to make the most of this special time with dignity, warmth and comfort. I encourage at least one of you to sit down and speak with someone from hospice. They know exactly where you are coming from.
God Bless you all.