Mac...my dad is deceased, but my mother is toxic to me also. I try to refrain from visiting as much as I can, though now she wants my presence, and thinks of us as always having had a loving relationship...NOT!!!
I think if you are happy and your children are happy also, and visiting MOM upsets you, then you too should avoid contact. I know, I KNOW, it's very hard to detach, and nearly impossible to detach completely...not suggesting that, but it seems in your case, distance is a good thing.
Seeker