I know how hard it is for you to keep your feelings to yourself especially about your daughters. But you must, do you have a friend you can vent all of this to? Do that or bring it here and then is you pray, then give it to God and let him guide you. It works!! It wasn't until I renew my R with God that I began to feel some peace. I am really not trying to preach here, it is just a suggestion.
Spend your time this weekend making it as fun as you can for your daughters. Whether you know it or not, H will be thinking of you all and feeling guilt without you saying a word to him. There will likely be some tension from the rest of the family because you are not there with him.
I found out a little while ago, that last year when H and Ss went to our usual vacation spot with his family, that H talked about m just about the whole week. That is when we had the touch and go, then he got involved with OW. I feel that it was because he was starting to realize what he had lost and he got scared because he wasn't ready to come home.
Everything happens for a reason, maybe Dad needs to find that it isn't better out there, he needs to realize how good he had it here. Maybe he will find God and that is the most important thing when he finds Him he will know he is supposed to come home.