Ok OP, I'm sorry this has happened.
harness the strength you had in telling him to go home.
you don't have to think about the future right now just the next two days, let's break it into steps.
do you have 2x breakfast, lunch, dinner for the next 2 days - if not, make a list of what you need. Christmas dinner can be roast chicken and veg, easy stuff.
Do you have presents for Christmas Day, if not add them to the list.
figure out how to go and get the stuff you need. Can 13 year old entertain the younger while you shop, iPads etc?
get cheap sweets and treats in the shops, tell kids you are going to have cosy quiet Christmas, 'Dad had to go see family, but you will see him after Xmas and celebrate then'
stay off social media, cuddle with your kids and watch films.
your calm and your panic will be very contagious to the kids, choose to exude calm to keep them safe. When fears come up tell yourself you will think about it after these 2 days.
he is in a safe place, no one is in imminent danger - stay off social media, it will be contributing to your panic.
you're ok and you will be ok, love and strength to you