eazybee ... What I do not understand is why the daughter and children could not travel to Canada at half term and surprise the ill, but not terminally so, Grandmother. They would have had more time to spend with her and not had to miss their schooling, which is more important than a birthday party, (which strikes me as the main reason the mother wants to go).
I understand it perfectly. An ill/ailing parent, or in-law, especially one who lives so far away, who is about to have a 'milestone' birthday, who may, or may not have the chance to see her grandchildren again, I would think is far more important than children missing a week or two of schooling. There is no mention of there being a 'party', just that it's her 'milestone' birthday. And if she's ill, there's unlikely to be a 'party' anyway. If there's a gathering of a few close relatives/friends, what better surprise for her than to see her grandchildren again.
A close friend of mine, who lives overseas, had to miss her own mother's milestone birthday earlier this year, due to flight restrictions. It caused a lot of sadness/upset, both for my friend, and her mother, neither who will be able to get that special time back again. Too many people have had to miss far too many important special family occasions/events over the past couple of years, myself included. I think she's doing the right thing.