I don't know if there's a way you can get the message across without triggering a shunning.
While we were fading, my mom knew we weren't being very spiritual and kicked up her "preaching" work to our sons. Any time she was minding our children it was like a nonstop Jehovah lesson.
"look at the birds, do you like birds? Do you know who made the birds? Jehovah did, because he loves you"
"You know about Christmas, did you know that it makes Jehovah sad, even though it looks like fun"
Stuff like this pissed me off.
As we were coming up on our first Christmas we sat our oldest down to talk to him about it. He was very hesitant about it. His comments solidified for me what effect my mom's preaching was having. He wasn't sure that he wanted to celebrate Christmas, not becuase it was wrong, or pagan or Jehovah doesn't like it, but his explanation was that it would make Nana sad and he didn't want to make her sad.
The whole message she was trying to teach him about Jehovah, didn't sink in, it was his Nana telling hm these things, not Jehovah so it was HER he didn't want to upset.
It was then that I chose to make things formal with my parents and told them I wasn't a witness anymore. My mom informed me that they would need to shun us but then wanted to make arrangements for us to bring our children over. They were just potential converts for her.
The end result is, when a child gets two different messages, it just serves to confuse them. While your mom no doubt understands that, she will need to decide what is more important to her, preaching to her grandchild or being a grandparent. It's well within your parental rights to ask her to choose. The down point is, without the ability to convert, will she then switch over to full shunning?
It always sickened me how easily witness parents could flip a switch and turn love into hate.
