I agree with this. Too right you should lose your shit at both of them. Ok, so you don't know her, but she knew he had a wife and children.
He is more accountable, but she is still accountable.
I'm so sorry OP, your world must be crashing down, and the one person you thought would protect you from that is the one who caused it all. You have already found your anger, and good on you. Don't worry about changing his profile picture, why the fuck shouldn't you! He didn't care about you so why should you care about his bloody reputation. Say it as it is!
I hope you get some sleep, at least so you can deal with the kids. Not sure what to suggest, being on holiday makes it so much harder as I imagine you don't want to even be breathing the same air as him right now.
If you want him gone, tell him to get a flight and go. You should call ALL the shots now and he needs to be doing exactly what you want when you want it. Can you tell the little one he has to go back to work urgently, some sort of work emergency? Failing that, i'd tell him to get another room and then he can take the little one out to some places on his own (tell little one you are not well?) just try and manage it until you can get home.
He has ruined your holidays and your childrens holiday, and all your lives, for what? Apparently someone who means nothing to him! Jesus.
And if you want to punch him in the face, its the least he deserves. I'd say go ahead. It won't be a fraction of the pain you are feeling right now. If he stays on the holiday, i'd also be taking his phone. Petty, but hell, he clearly isn't responsible enough to use it.
In fact if you get through the holiday and he is still there, I'd through his fucking passport in the sea on the last day, leave and let him deal with the headache of getting himself home. And while he does that, get your ducks in a row at home before he returns.
You sound, from your updates, like an incredibly strong person. You may not feel it, but you've already found your anger. You'll get through this, just take it hour by hour and day by day. I'm so sorry you are going through this.