Comatose - You were so very helpful to me when I had a family issue last year. I wish I could return the favor with splendid insight that would make your current situation easy.
Sadly, I cannot.
I tend agree with those that say it is more damaging a child to see their own parent treated with disdain - or worse, treated as if non-existent/dead.
I can tell you, though that some JW grandparents (even some that are prominent in the org) find a way to be civil to their DF siblings and have/maintain relationships with their grandchildren.
Sometimes it might lead to elders stepping 'aside'. Sometimes not.
Either way, it's a crappy deal for all involved. Damn Cult.
-Aude.