Hey it sucks and nothing I can say can change that. I do have idea of what you and your family are going through though my dad lost his arm at the elbow in an industrial accident.
I'm sure you've heard this but prosthetics have come a long way as well has physio therapy and occupational therapy. Whatever you do take all the hell and assistance that you can get, these people will ensure your success in the future.
The other thing is your allowed to feel sad, mad and depressed, seek out those that will listen, those that have similar experiences, it will help.
Your life will be different that's for sure, but it's really up to you how good it can be. I've known people who've lost limbs that do more now than before they lost them, It sort of gave them a license to try new things.
I'll be thinking of you.