JW's can't help but talk about their religion and if they think they can save their grandchildren, they have to try.
I left when my kids were 5 and 8 years old, when they looked after my children I would make sure that after the visit with my parents, I will explain to my children how the JW's are wrong and to have compassion for my family as they are under mind control. and I explained to them how free we are now that we don't have to follow any man made rules.
We still need our family and I have now learnt how to have a relationship with my parents, If my dad tried to preach to me I decided to research and give him bible answers that would disprove his way of thinking, religion does not come into our discussions anymore, I think they have decided not to bring it up anymore and that I am a lost cause but I know they still love me and my family, And that all that matters.