Hiya.
What are you most worried about in the meeting?
That they will say things about DS that H picks up on and has a go about?
I think you need to make a contingency plan. Keep to the 'positive' list - but if you come out of the meeting and H is worked up and cross, IN NO WAY agree to collect DS straight away. Why not agree in advance that his gran keeps him until bedtime?
Ask in the meeting how, in their opinion, you can best support DS at home - surely they will say lots of encouragement, boost his self-esteem etc.
And TELL H that you will not let him see Ds if he is all angry with him. Remind him of his promise at the w/e, and if he doesn't stick to it, either go and stay at your Mum's with the kids ot tell him he can't speak to DS until he agrees to be sensitive.
I was thinking about this this morning - I know you have told him he won't go to a naughty school, but IMO it is important you do this IN FRONT of H, not afterwards when H has stormed off. If DS sees you also afraid to speak out in front of H it actually fuels his fear that H and his threats ARE to be feared.
Sorry if I'm teaching you to suck eggs - feel like Natt with her 'who am I to say...' etc - just trying to give an outside perspective.
if the meeting is confrnting, in terms of teling you how bad DS is suffereing because of his self-esteem etc, it will at least be further evidence as to why this man needs to change fast, and NOW, or you have to get the kids away from him before more damage is done.
I really am sorry you are having to go through this.
Bravers on....