Dear Riverwatch,
Let me share some good news for you!
I have friends who have "wordly" parents, they have always stayed in touch with them and take trips with them and to see them. They LOVE them and wish only good things for those parents. You can sort of give your son a place to go that is not full of JWism when he needs that. The key is to let him come to this on his own, he may stay a witness forever, but he will always love you. I think your kindness to your daughter in law will never be forgotten and create a special bond between you to; however, please be sure not to sound like an apostate when talking with them, by this I mean, as you learn things on this board and others you will learn things that JWs don't know to much about, and if you bring those things up to loudly or to often you will be labeled bad association.
Your grandkids will also LOVE you especially if you are a kindly person, which you seem to be. I know of plenty of grandkids who travel to see "wordly" grandparents, your son may even allow you to give Christmas gifts to them, although I would be careful about ever taking them to a church service, this would really set them off. I have wordly aunts and uncles and really love them, wish I could of spent more time with them. The upside to your grandkids being raised as a witness is that for the most part they will be taught to be respectful, this of course does not happen with all the young ones but it is taught and encouraged.
I know this is not what you would of wanted for your son, but, I have learned as well in my life is that your kids grow up and make their own decisions about things and not all of them are ones we would have like to see them make.
Hang in there, and hopefully you will see that you can still have a close relationship with your son and daughter in law and grand babies.
Sincerely,
OC