This is just such terrible news for you and your family. I can understand you are heartbroken for your son. All you can do is be there to offer support and help when you can. Encourage your dil to make lots of wonderful memories with her young family. Try to keep hope that medical advances are happening all of the time, so do not give up hope. I hope they happen in time for your dil.
I've got another 'keen'... Ouch!