OK here goes. Trying to keep it as brief as poss.
I had very controlling parents. My former therapist described them as extremely narcissistic. They controlled every area of my life. They did this by being physically abusive and also being incredibly emotionally abusive. On two occasions when I was a teenager living at home, after I disagreed with my father and had a mind of my own, he stopped talking to me for four months at a time.It took me a long time to emotionally break away, but I did so in my mid-to-late 20s, well before starting my own family.
I confronted them with the abuse when I was about 30. They denied it and said I was delusional. They stopped talking to me (again). I had DD. My mother wanted to see her. Eventually, some years later, I said she could provided she heard me out. She did. She still denied stuff, but I wasn't buying her bullshit any more and I was able to express what I felt about her and my father's parenting. I agreed that she could see my DD provided that she treated me with respect. We agreed we would try and have a relationship as adults. It is important to mention here that my parents, but especially my mother, treated my brother v differently, i.e. they didn't abuse him.
So for the past few years, my mother has come about once a month to see my dc. She hasn't asked, but I do not let her take them out on her own (except to the park which literally backs onto my garden so I can see them from our windows).
My father has met my dc at family gatherings but as he is still not really talking to me, my children have never been to my parents house or seen my father more than a couple of times a year, if that. On all these occasions my father has been rude/aloof/downright odd/bullying towards either DH or I. On the other hand, he has been a delight towards the children and DD really took to him.,
Earlier this year , after my father was extremely rude to me at a family gathering and my mother yet again let him get away with it, I decided that I would no longer go to any family gathering if my father would be there. DH agreed with this. It was difficult, but I explained this in simple terms to my DD and she understood 
. I also told my brother by way of explaining why we wouldn't be at my niece's 1st birthday party.
Anyway, I really struggle emotionally at Christmas because of my family situation. I always feel a loss so keenly. Although my mother and I have a relationship now, I have really moved on emotionally and I just can't engage with her. She knows very little about my life, and it is a struggle for me to talk to her when she's over sometimes. I am always polite though, because I believe in treating people with manners and respect as a matter of principle, and particularly in front of my children. Inside though, I still have a lot of anger and cannot comprehend how she could treat her child like that - feelings that are only growing as DD does.
My mother would like a closer bond with me and has tried to do this. To be fair, she treats me with respect now and is complimentary. She keeps offering to take me out for lunch and I've been once or twice but I can't give her more than polite chat. I've just switched off. She is, I have to admit,a very good grandmother within the limitations I have set. She would adore to see my children more, and often tries to, but I subtly keep it at once a month or so. She spoils them with presents.
So, my issue is that this Christmas me, DH and the kids are going away for a massive Christmas holiday to fab places. We'll be away nearly a month. We so need this after a very difficult year and it's an important break for me and DH emotionally - it has big significant meaning.
Part of the reason we chose to do it is because we (DH and I) both really struggle at Christmas. DH has an actively difficult mother, whereas I have a dormantly difficult mother 
and an incredibly difficult father. Our sibling relationships are also strained on both sides.
So while my brother and his family go to my parents' for christmas, we never get invited. I have to say, I feel very bitter about this. Not because I want to go - I really don't! - but because it's just not fair, not fair, not fair. I'll never get over the unfairness of how I got the shit and my brother didn't.
I haven't told my mother we are going away, even though it's been booked for ages. She has been trying to arrange a time to come and see the children the past few weeks and I've put her off. Mostly because it hasn't been convenient, and with us going away in under a week, time is limited. However, I am also feeling very emotionally stressed and low at the moment and am just hanging on until our break. So I haven't felt emotionally strong enough to see her, even though she does 'behave' herself and is there primarily for the children. I know she is annoyed that I'm saying 'no can do' to her visiting before Christmas. She wants to see the kids and give them their presents.
For some reason, I am reluctant to tell my mother we are going away. Part of me really wants to just go, and then when she contacts me next week to arrange a time to come at some point, just text her back saying 'sorry, we're away until January'.
I know that it's kind of childish to go off away for a long time at Christmas without telling her. On the other hand, I WANT to punish her, I want to be a teenager saying 'nah nah, you can't catch me or know what I'm doing or where I am'.
I hate that she was so controlling. And when I have gone on holiday in the past, she has always stored away in her beady brain he exact details of my dates away, and calls as soon as she thinks we'll be back, and KEEPS calling. I would fudge my dates, and then find she'd be calling several times a day for days. I did make my annoyance about this known, and although she didn't apologise, she did switch to texting as her way of communicating me instead of calling.
I do want her to get the message that I have my own life now and she has no right to know the details. I do want her to realise that she has no real 'right' to see the children. I know that part of why I'm annoyed is because she will see my brother and his DD on Christmas day, but my children have to be seen on her own at some other time.
So I want to go away then let her see the kids soon after we get back. Telling her we're going away is going to be irritating. She repeats everything I say, which I find incredibly annoying. She will ask lots of questions.
On the other hand, she has been a decent grandmother and they do both adore her. And it is a bit shitty to not let her see the kids before Christmas when we'll be away.
Although from their point of view, as they just had a Christmas gathering and present exchange with DH's family, and will get presents from us, it might be nice for them to see my mum when we get back and get their Christmas presents from her then so it's spaced out.
Phew. That was long. I guess what i'm asking in short is: AIBU to bugger off with my kids abroad for Christmas without telling my mother, and letting her sweat it out?