While I can applaud your effort to take the high road and act in love, my worry would be your innocent children. Personally I think it unhealthy for children to have to come to the knowledge and experience of the very conditional yo-yo love of jw grandparents. Today grandma/pa love them, tomorrow? who knows what the borg will require. Should a child be required to live by the rules of this cult even if they are not members themselves? or do/will you explain it as a mental illness of sorts or go into how cults work? I am truly asking not being sarcastic.
Families are or should be package deals, warts and all. We all have our faults but if my kids are threatened either physically, mentally, spiritually or sexually, look out, this mama bear will not stand for it. Just my take. I can say this because I went to extreme lengths to protect my kids and that of family members from my own jw, who I do love very much. We all love him, but will not tolerate any jw shenanigans. Things are better now and luckily all the little ones have grown up and know the dangers of the jw's from me, books, their own churches and their own research.