It's very sad this new situation. I don't know the distance between your location and where they are heading to? Can you consider relocating half way?.
How long before you both retire? Some retirees like caravanning and visit for a few weeks at a time perhaps on their way to a holiday destination.
I'm aware, being ex Defence person, the hurt family members go through in similar situations. So it is common but that doesn't help you. I did know of a father of a young family with children. He loved his grandkids so much he'd follow them around Australia and resettle just to be close by.
I'd be interested in other members ideas.