I only had a couple ideas as I considered your request:
1. If you are LDS, give your son a blessing and maybe schedule an appointment for your son to visit with the bishop or an LDS Family Services counselor so he can talk through his emotions with someone removed from the same shock.
2. Show him how to rebuild one brick at a time. Maybe get a small, table Christmas tree that you can keep for years to remember the rebirth of family Christmas traditions and a 2020 first Christmas ornament and some candy canes to decorate the tree and symbolize the beginning of your temporal and emotional rebuild.
I'll let you know if I have any other ideas. God bless!