In my case, my parents have more to fear from my teenage children. They've left my parents more than once in tears of frustration after a day with Grandma and Grandpa because they fairly easily dismantle my parents attempt to convert them.
I have two brainy rational kids...they have a whole set of questions that JWs just can't answer. I've heard them discussing it, planning what they'll ask if they're asked this or that.
When we lived near them, I've had to go get them early a time or two because my mom in particular just can't take it anymore. My kids are always respectful and well behaved, they just don't put up with the brainwashing. They give it right back to the grandparents, just asking their questions.
Last time, it was about the blood transfusion issue. My oldest daughter had my mother in tears in about two hours after her attempt at indoctrination on this point and my daughter called for me come to get her because Grandma was so upset.
She asked my mom, "Why can't you take whole blood when you can have factions made out of every other part? That's like telling me it' s wrong to eat a sandwich, but it's fine to eat bread, meat, cheese,mayonnaise, pickles, tomatoes and lettuce separately."
My mother had absolutely no answer to this, so did some emotional coercion about "Oh, I don't want you to die if you take blood!" and my daughter just said, "Statistically, I'm more likely to die if I don't." and finally my daughter just got up and called me to come get her.
She wasn't invited over again after that...not alone. *G*
When they were smaller, I'd leave them with the grandparents very infrequently. My dad doesn't indoctrinate and he'd usually take them somewhere with him anyway, because to be honest, my mom can't stand her grandkids for very long most of the time anyway.