How old is your son? You may need to limit his association with grandparents to times only when you will be supervising.
You'd be amazed at what JWs will do to children behind your back. I don't mean that to be harsh, only realistic. I
I was shocked to hear of the emotional abuse my children's father inflicted on our kids while they were growing up. The sad thing is, I didn't learn about these abuses until the children were grown. My oldest is 29 years old and still struggling to get his fathers approval....he's still with the Borg.
The other three have very little to do with their father...very sad. (Their decision)