If I recall, your situation is a bit similar to mine. Your parents are near 80 or so, you have 2 brothers and 2 children. My parents are just turning 70 and I have 3 children. You were never a JW but you didn't see it as the truth when you looked into it. They won't want to purposely hurt your feelings the way they would if you had once accepted it but now reject it. In either case, they also wouldn't want you to think that JWs can't act normally. You already know that they aren't normal, but they don't know just how non-normal they are.
My parents realized they were never going to convince me to come back, but they still don't want to appear too cult-like, especially to the grandkids, and, in fact, some exJWs who want to continue to have a fairly normal relationship can play a game on JW parents if they wish to continue a relationship. One of the attractions of the JW religion to JWs is that it appeals to a pride, a sense of importance among the more educated world around them. Therefore, their own ego can be played to get in the way of Watchtower rules. (Some JWs play on this very forum for the same reasons.) If they get a feeling that you actually feel sorry for them and are conveying a very sincere message to others about them personally that they act brainwashed and can't think for themselves, then they will act on that to defend themselves. I believe it worked on my parents and I've tried to make the most of my opportunities with them to turn them into normal grandparents, to the extent that my children have even received "winter-time" gifts from them. My kids could care less about their JW religion, and therefore the situation works out nicely. My kids don't have to go around feeling they have no grandparents, when other kids talk about their own grandparents.
Another thing about parents, of course, is that it's hard to erase natural affection completely. Your parents have been JWs for 30 years or so, which means they probably never expected to die in this system, before Armageddon. When they begin to realize they might, many of them will start to want to see their kids again. I know of a couple situations where older 2nd and 3rd generation JWs have started collecting family pictures and looking at family genealogies and histories they never cared about before. Even though they are still JWs it shows that a recognition of mortality is getting stronger. This recognition can make them want to be closer to their own children and grandchildren.
Whatever it is, make the best of it. Time passes much too quickly.