Curl,
Welcome.
I was waiting for the blow up from the time I started to read your post (have narc relatives) and there it inevitably was. You were set up for that good and proper by them.
I would agree with Meerka's response particularly with regards to you having counselling. BACP are good but there are caveats. You need to work with a therapist that you can actually work with and also someone who has no bias about keeping families together despite the presence of mistreatment.
I have previously found this excerpt most helpful:-
"There's only one way to get decent treatment from narcissists: keep your distance. They can be pretty nice, even charming, flirtatious, and seductive, to strangers, and will flatter you shamelessly if they want something from you. When you attempt to get close to them in a normal way, they feel you are putting emotional pressure on them and they withdraw because you're too demanding. They can be positively fawning and solicitous as long as they're afraid of you, which is not most people's idea of a real fun relationship.
I always have the problem that I get fed up and stay away from THEM long enough to forget exactly what the trouble was, then they come around again, and every narcissist I've known actually was quite lovable about half the time so I try it again. (I do not do that any more).
A clue: Run for cover when they start acting normal, maybe expressing a becoming self-doubt or even acknowledging some little fault of their own, such as saying they now realize that they haven't treated you right or that they took advantage of you before. They're just softening you up for something really nasty. These people are geniuses of "Come closer so I can slap you." Except that's not the way they think about it, if they think about it no, they're thinking, "Well, maybe you do really care about me, and, if you really care about me, then maybe you'll help me with this," only by "help" they mean do the whole thing, take total responsibility for it, including protecting and defending them and cleaning up the mess they've already made of it (which they will neglect to fill you in on because they haven't really been paying attention, have they, so how would they know??). They will not have considered for one second how much of your time it will take, how much trouble it may get you into in their behalf, that they will owe you BIG for this no, you're just going to do it all out of the goodness of your heart, which they are delighted to exploit yet again, and your virtue will be its own reward: it's supposed to just tickle you pink to be offered this generous opportunity of showing how much you love them and/or how lucky you are to be the servant of such a luminous personage. No lie they think other people do stuff for the same reason they do: to show off, to perform for an audience. That's one of the reasons they make outrageous demands, put you on the spot and create scenes in public: they're being generous they're trying to share the spotlight with you by giving you the chance to show off how absolutely stunningly devoted-to-them you are. It means that they love you; that's why they're hurt and bewildered when you angrily reject this invitation.
There's no middle ground of ordinary normal humanity for narcissists. They can't tolerate the least disagreement. In fact, if you say, "Please don't do that again it hurts," narcissists will turn around and do it again harder to prove that they were right the first time; their reasoning seems to be something like "I am a good person and can do no wrong; therefore, I didn't hurt you and you are lying about it now..." sorry, folks, I get lost after that. Anyhow, narcissists are habitually cruel in little ways, as well as big ones, because they're paying attention to their fantasy and not to you, but the bruises on you are REAL, not in your imagination. Thus, no matter how gently you suggest that they might do better to change their ways or get some help, they will react in one of two equally horrible ways: they will attack or they will withdraw. Be wary of wandering into this dragon's cave narcissists will say ANYTHING, they will trash anyone in their own self-justification, and then they will expect the immediate restoration of the status quo. They will attack you (sometimes physically) and spew a load of bile, insult, abuse, contempt, threats, etc., and then well, it's kind of like they had indigestion and the vicious tirade worked like a burp: "There. Now I feel better. Where were we?" They feel better, so they expect you to feel better, too. They will say you are nothing, worthless, and turn around immediately and say that they love you. When you object to this kind of treatment, they will say, "You just have to accept me the way I am. (God made me this way, so God loves me even if you are too stupid to understand how special I am.)" Accepting them as they are (and staying away from them entirely) is excellent advice. The other "punishment" narcissists mete out is banishing you from their glorious presence this can turn into a farce, since by this point you are probably praying to be rescued, "Dear God! How do I get out of this?" The narcissist expects that you will be devastated by the withdrawal of her/his divine attention, so that after a while a few weeks or months (i.e., the next time the narcissist needs to use you for something) -- the narcissist will expect you to have learned your lesson and be eager to return to the fold. If you have learned your lesson, you won't answer that call. They can't see that they have a problem; it's always somebody else who has the problem and needs to change".
There is really no going back from this because you will keep being on their receiving end.
I would also seriously consider keeping your children too well away from them as of now, particularly your mother. NC is an option but one that you cannot countenance at present. A good rule of thumb here is that the parent is too toxic/difficult for you to deal with they are far too toxic for your vulnerable and defenceless children. You only see them for your children supposed benefit anyway (they will not benefit); its not a good enough reason at all to keep seeing them and subjecting yourselves to them. Seeing a narcissist interact with their grandchild is painful, mainly because there is no interaction. Its like watching a re-run of a tv show you've always hated.
Its not your fault she is like this and such women always need a willing enabler to help them.