Agree with MrsC although I totally see where you are coming from, OP.
It's horribly difficult to say bye to my lovely DDs and send them off with abusive ExH for the week. He used to see them at weekends, but now just one year post-separation it's fizzled out to school holidays only.
The DDs still love him very much (they are young) and I loathe him and the way in which he has slowly and deliberately crushed me over the years.
I have been telling the children to enjoy their half term with daddy and enjoy it etc and getting excited on their behalf.
They know full well that daddy will let them watch to all day and will only take them swimming if mummy has packed everything for them, will not allow them to visit their old school friends etc.
Like you op, he lives in the marital home and as yet has not paid a penny towards them.
I make a point of going out to his car and kissing all 3 DDs and smiling a lot, waving them off etc. He generally skulls and stares at the floor. I want the DDs to feel happy and not guilty for going or for loving their dad. I also want him to know I am strong and not afraid of him anymore.
And ultimately it makes me a better person than him. So I win.
Having said that, nobody should be criticised for hating and not wanting to speak to their abuser. You sound like a good mum, your son is loved, I don't think you need to play happy families if you are not ready for it.