Hello Dragonfly. I already provided a few thoughts about this in a previous post about your Thanksgiving(I had not read this one yet). So I won't reprint it all, but just add a couple of more thoughts.
He may or may not suffer from bipolar, or he may have just a mild case, or he may have depression or anxiety problems that cause him to drink too much. I use the word "may" a lot because I'm not in the position to judge. However I can understand your worries.
In my other post, I provided some links to some articles and perhaps if you can get him to read some he may see something that he may recognize. Our off spring certainly don't want to think that they are as bad as we were at our worse. On the other hand, you must have provided quite a few good moments otherwise he wouldn't be talking to you.
I didn't mention it in my prior post, but you may want to advise him (gently) that he may not have anything wrong other than drinking too much. Alcohol does provide short term sedative or escape from our problems, but in the long term it can be a depressant as well. In fact long term heavy drinking almost always causes anxiety and/or depressive problems.
It's an easy trap to fall into. Have a few beer, feel good, have a few more feel better. Later in the week feel anxious or depressed, have a few more beer, repeat multiple times and suddenly you need a few drinks just to feel not anxious or depressed. However most people do not realize this, especially if they are around other people who like to drink too.
His kids telling him to stop smoking, hasn't made him quit smoking, his kids telling him that he shouldn't drink probably won't make him quite drinking.
Will his kids follow his example and drink too much? You can hope not. Some do, but a lot of kids that I know who were raised by parents who were always passing out or making fools of themselves from drinking, don't drink much. They saw the bad effects.
However as your grandchildren get older you may be wise to provide them with some brochures on mental illness and how to get help if they notice any of the symptoms. Take Care. paul m