Has your DH ever called them on their behaviours before - or does he expect you to just suck it up?
If he has known about it (especially seen it) over the years and not stepped in then he doesn’t have a leg to stand on.
I think that an overnight at xmas is not the time or place to have this aired and you shouldn’t go. You could ask him to facilitate a conversation at another time where the behaviours are highlighted and listed and declared that they won’t be acceptable and if they happen your DH will up and leave with you.
Would he do that for you?
Do you want him to?
Given their ages and that the hostility is less overt now they may choose to change if your DH shines a light on it.
However it may be too little too late for you and that’s your choice.
Also as they are now adults are you comfortable calling them on behaviours.
Would your DH back you in this?
Someone posted the “shine a light on it” technique for bullying which goes like this:
“It makes me feel very uncomfortable when you snigger and whisper like that - is that your intention?”
You are very traumatised - even if you choose never to cross paths again - you will need to deal with this for your own sake.