Im probably gonna get flamed for this but I personally wouldn't do anything.
Can you believe I just said that? My reasoning is that at 80 years old, your grandpa is probably too old in the tooth to wanna change. Does he still drive? That would be my main concern but if not, let him be. He has no doubt worked hard in his youth, seen things we will never see and is still around to tell the tales.
My stepfather is a happy go lucky functioning alcoholic (seems sober) and we have tried to wean him off more times than I care to remember. At his age, with the length of his habit, his quality of life would be rubbish as his cravings could consume the life he has left.
You can mention it and ask his thoughts on the situation but at 80 years old he may not be too open to ideas and suggestions.
Sorry if I frustrate people with this reply but it is just my opinion, a younger person could change their ways easier or focus energy into something else. At 80 and still functioning and active (walking dogs etc) I would just let them enjoy the few years left on earth. Your grandpa's wife should be a pro at nagging your gp by now so i'd leave it to her to sort him out.
Easier said than done and I appreciate that I do not love these people like you do but, at that age I believe people have paid their dues and have been on the planet long enough to do what makes them happy