How old is your daughter? If she's a toddler, I think you should behave as if everything is normal. I would take them to her grandparents' house and behave normally, but I would not leave her to them because, as I heard Dr. Laura once said to a caller with a JW mother-in-law, to them ultimate salvation can only come by being indoctrinated.
If she is older, does she believe the JW doctrine herself? Does she want a relationship with her grandparents? If she has not been duped by the JDubs, I would instruct her to let her grandparents ramble, to tell you what they said, and then instruct the grandparents to back off if they want to see their granddaughter. Your daughter's feelings need to be considered. If she doesn't want to be preached at, I wouldn't force her.
Most of all, educate your daughter about brainwashing, cult-think versus real thinking. Help her to have an open mind and to accept people where they are and not try to change them, but, at the same time, not allow them to change her. Encourage her to reach her career and educational goals and offer her what help you can. If you can't help her when she is having a problem with school or psychological issues, please get outside help.
All the best for a happy future! Welcome to freedom!
Mum