I am so sorry. What a tough situation.
However, this is incredibly unfair and horribly passive aggressive:
They are both career minded and have already given the GCs to others to raise ie. nanny, childminder etc. The DIL said she would be a stay at home mum, then when the darling GCs arrived and the reality hit she soon went back to work
No, they haven't given their children to other people to 'raise' - they've done what millions of working parents have to do, or indeed WANT to do, and continued their careers. It's the norm. There could be many reasons for your DIL to choose to go back to work instead of SAH, and it doesn't take a genius to think that if they're emigrating as the answer, financially it might have been a no choice situation for her to work anyway.
If this is the way you think of them and these are the kind of pass-agg 'digs' you make in your head, then it sounds that there isn't much love lost either way really. And if that was the situation, then it doesn't automatically change once kids come along - you feel a new link and a pull, but they don't.
Skype is the way, it's not the same though.