Nonnie
1. "To expect a man to use the courts before he has tried every possible means to get contact with his children in naive."
But the OP mentioned nothing about her sons either trying to gain contact or exhausting every possible means out there. What's "naive," in my opinion is a grandparent who holds onto the expectation that an ex-DIL (who according to them has just broken up with their partner of 9 years) will go out of her way and facilitate traditional holiday plans as usual. As if nothing very drastic has just occured in both hers and her childs life. Divorce can be extremely hard, stressful and devastating for anyone. OP should given both ex-DIL, her son and her grandchild some time to adjust to their new family dynamics, before branding her ex-DIL as a potentially spiteful woman with the potential to brainwash her own child - solely for she expected her holiday tradition to continue as usual - in spite of the obvious shock and grief that this seperated family may currently be facing.
2. "Can you imagine how difficult such a woman could be if there was a court order? "
The judges have seen and heard it all. Nowadays women loose custody of their children when they continuously violate court ordered custody agreements. Ofcourse there are few exceptions to this rule. Secondly, this argument can't be used as a justifiable means of not going to court and doing things the legal way. She has 3 grandchildren whom she unfortunately doesn't get see. And from her story at least two different ex-DILs. Her sons at some point will have to take some legal responsibility if they want to visit their children, as opposed to relying to the "spiteful woman," narrative. If her sons won't do it, then she should remain neutral and try to form an amicable relationship with ex-DIL. One that would allow her to see her grandchildren occasionally. Before trying to do this, don't let your anger/emotions lead you to stereotype your ex-DIL this way.
And yes women can be extremely spiteful - no one is denying that. But so can men so this cant be used as a justifable lable. Bottom line is if this breakup has just occurred, then OP should step back for a while, refrain from taking any sides in this seperation, withold any anger/emotions and simply give this whole seperation and visitation schedule some time to settle. It maynnot have occured to her that ex-DIL may be grieving, depressed or maybe chosen to rely on her own support system for some healing - before exposing herself to a family that she was once a part of. Maybe her own son is equally depresed and grieving and could'nt care (at least for now) about his mothers visitation schedule/holiday traditions with his children until he too experiences some form of inner healing. Not sure why it has to come down to the grandparents asking " what have we done to deserve this," when its very clear that they are dealing with a family unit that's probably in complete chaos (emotionally at least) right now. You should be a source of support if you can as opposed to getting upset with ex-DIL and stereotyping her. Sorry but maybe with all thatrs going on right now you as grandparents have just been put in the back burner until they can clear their minds. It may also be extremely hard for anyone of them, including your grandchild to be in any celebatory mood with all that's going on.
In the event that ex-DIL becomes difficult, then then the only other option to her seeing the grandchild would be through her son - and only after he goes to court, or if either one of you works out something amicable with his ex-ewife/DIL.
Give the dust a little more time to settle - the open wound of divorce/seperation is all too fresh to make any stereotyped assumptions (especially if you got along great with ex-DIL as you say). I wish you the very best.