My sister has shunned her daughter since she was disfellowshipped six years ago, at the age of 18. In the meantime, my niece had a daughter and she allowed her parents to see the little girl once a month. They picked her up and spent the whole day with her. My niece had been very clear that she didn't want her parents teaching her daughter anything about the JW religion. She thought things were working out OK until a few months ago, when her parents started to ask if they could take the child out in service, if they could read the bible story book to her. etc. She said no. They could read her version of bible stories, but not the JW version. They could NOT take the child out in service or to meetings. About a month after this conversation, she received a letter from her parents. The letter said that if they couldn't teach their religion to the granddaughter, they couldn't in good conscience continue to "associate" with her. In effect, they're now shunning a four-year-old child!
Needless to say, all association has ended. My niece is now pregnant with her second child, and she hasn't even informed her parents. All along I've had the opinion that to let her parents see her child while they continued to treat her like a piece of dirt was wrong. What does this teach the child? That her mother has no worth. That it's OK for people to treat her mother this way. That's not what I would want my children to learn about me. It's all about setting an example for children about human dignity and worth.
I vote for not allowing the grandparents to see your children until they can treat you like a decent human being. You don't want to send the wrong message to your children--that this kind of behavior is acceptable. It isn't.