Hi - I'm sorry you saw your kids upset like that. They are trying to deal with the situation too. The outburst was probably just stuff bottled up and finally let out. Wait a few days for the emotions to die down a little and then try and have a quiet conversation. It is not healthy for anyone to bottle things up. That is where resentment starts. Same rules apply I guess. Validate but don't take responsibility for things that are clearly not your doing.
Re your H. I can see why you feel that it was a [censored] move on his part to speak to the kids first before you. I would give it the benefit of the doubt and hope that it was a spontaneous discussion on their part instead of something planned. You are right. Your kids are not little anymore and the days of being woken up at five in the morning by very excited children eager to open their presents are behind you. You response was appropriate and considerate. However, I would question what your motives where for saying no? Was it to because you don't feel it is right anymore having him in your house or was it to shove in his face the consequences of his actions? BTW - I completely understand both of those feelings. I do not like having H in my house as I feel he is intruding and I want to shove the consequences in his face. But, for me there is a third ... I still want to feel like we're a family sometimes.
Anyway, don't beat yourself up re the invite. Focus on your kids. Even though they're grown up now, they are obv. still hurting.
