Glad you had a great time with your sons. Your family sounds wonderful, and I wish you lived closer to them.
About the 'other' side of the family, I think you are partly projecting your hurt/anger onto them. But I also think they could have done more to see your sons while you were so close. I don't think its as much of 'writing you off' as it is putting blood first and feeling uncomfortable around you. They aren't quite sure what to do, I am positive about that. They are in new roles, just like you, learning to live with this.
I am sorry you wasted all that time, but you did do the right thing by making the effort. I wouldn't even bring any of it up to W, I would just say (if asked), "We tried but everyone was busy, but Grandpa enjoyed our visit" or something like that.
