Yabvu to continue exposing them to this twat!!
I also have an abusive father who tightly controls my mother so I DO know where you're coming from to a degree BUT I very much controlled the VERY limited access he had to dd growing up, he wasn't allowed within 6ft of her and he KNEW if he ever said anything remotely inappropriate he wouldn't have seen her or I again.
YOU need to be your children's advocate and protect them - physically and emotionally.
If they don't want physical contact with him they don't have to.
Frankly in your position I wouldn't be taking them there anyway and I'd be very clear about why!
You DON'T Have to stay over on visits, stay in a cheap hotel or make it a long day trip, collect your mother or if she's up to it she could get public transport to stay at yours.
DEFINITELY no to them both coming for Christmas or indeed any other time. As pp says their home should be safe and comfortable NOT somewhere they are on edge and feeling unsafe.
My parents have NEVER stayed at mine and only mum has visited, she was never allowed to babysit dd as frankly I didn't trust her on safeguarding matters particularly regarding my father.
She's moaned about that sometimes but tough, dds safety was the priority.
You don't mention any sexual abuse of yourself but do you have any siblings? It's a myth that a man who abuses one child this way abuses all his children this way - just like other paedophiles they can have preferences or they avoid abusing the ones most likely to tell!
I also sympathise with the frustration of your mother not leaving him. Same here but almost 50 years. I've given up now. Mum knows IF she ever decides to leave him she will have my full support with whatever she needs but aside from that we don't even discuss it.
He has her completely convinced she wouldn't cope without him. Plus as a Catholic there's a LOT of guilt involved not just re marriage being a sacrament but also as she is now his carer and if she left nobody else would care for him and he wouldn't have "strangers" come in. Covid has made things so much worse as he's high risk and won't let her leave the house at all now! Awful situation!
Why has your mother decided to stay with such an awful man? such an ignorant and callous comment! Because she is a victim of long term and serious domestic abuse! Effectively she's been brainwashed.
Years ago Oprah did an interesting episode which began when the audience were queuing to get in to the studio. There were a few crew members planted among the audience who began to comment on a "nasty smell" once the audience was seated Oprah apologised for the smell and asked how many had noticed it while waiting - well over half the audience raised their hands! And that was merely the suggestion planted by people who were strangers to and had no power over them!
Oprah then admitted it was a set up and explained it was to illustrate how powerful it is when someone plants an idea in your head.
She then said something like "now imagine, instead of a smell it's your partner/spouse or parent telling you EVERY DAY that you're useless/ugly/stupid and you can see how abuse victims come to believe this is true"
This is what abuse victims have drummed into them all day every day by someone that at least at one point they loved and trusted! It's relentless and the hardest type of abuse to resist.
Lots of suggestions to meet the mum alone and that may be possible for op it wasn't for me because the secrecy puts my mum at risk. She cannot risk lying to my dad or angering him by having a relationship with me with him completely cut out. So I have a vlc relationship with him to make it easier for mum to stay in contact and have my support.
This IS his best behaviour believe or not. I believe you op
Why can your Mum not meet you at a local cafe close to her?
Does he follow her everywhere she goes?
Men like this track their closest victims movements, i suspect like my mum her movements are watched like a hawk! If she's so much as 5 mins later than usual back from dentist or shopping she's interrogated and accused of all sorts! Mileage is checked if they drive, constant phone calls/texts "where are you?!" Endless grief if they ignore the calls/texts...
It's not weak op it's an incredibly difficult situation.
I saw a counsellor but she told me to forgive my parents and see them because not seeing them was upsetting me so much! How on earth do you find one that understands this kind of family dynamic? where did you find this counsellor? Unfortunately "counsellor" is not a protected profession - meaning ANYONE can call themselves one and sell their services.
Good luck op do all you can to be strong and stick to your decision.