There is no fool like an old fool, and yours is selfish and cruel too, quite a turd in fact.
LOL at 'family time' and going on the holiday. He wants to have his cake and eat it, mainly to make himself feel better about the horrible thing he has done to you and to his own children.
Do you have a solicitor?
You need to get custody and visitation and child support set up asap. Also decisions made wrt the family home.
You need to have a clause inserted into any visitation agreement that there is to be no bad mouthing of the other parent or their family while DCs are with him or with you.
Looking forward, would you like to move closer to your own family? Talk to a solicitor about this, and of course you have to take the DCs' school situation into account.
What I did on the long, long weekends when my DCs were with exH initially was eat lots of chocolate. This isn't sustainable. So I decided that this would be time I might try out a vegetarian recipe just for myself, set aside time for reading or listening to music, get out for a long walk, reorganise a closet, or something else that I could feel positive about. It's really hard to get yourself together when it has all just happened though. Be patient with yourself. You won't have energy for quite a while. It will take every ounce of strength to get through each day.
Don't feel you are inadequate in any way. You are facing a situation like a sudden bereavement, and you need time to mourn. Be kind in your thoughts toward yourself and be kind in your actions - make a cup of tea, enjoy a few biscuits, get your nails done. If you have time, go and get a massage. Above all, have friends and family around as much as possible.
Christmas is going to be especially trying this year. 
Take it one day at a time.