You have the right idea, in my view. The children need to be protected from negativity, and that's essentially what your mother is throwing out there. I would try to go on with my life and see that the children have activities on weekends that will give them opportunities to learn new and interesting things: ball games, zoos, swimming, places especially for kids to have fun with parental supervision.

Your mother needs help. She probably is bipolar herself and refuses to admit it in
which case it could get worse. Your own family now should be your priority and
I wouldn't hesitate to see to it that if she tries to interrupt your life again not having had help, you will refuse to permit the children in that house.
And I would keep it that way until she agrees to undergo psychotherapy and sticks
to the schedule for appointments.

Take care of yourself first so that you may care for your children. I hope your mother is able to see her own problems and ask for help.

Rely on your husband's advice if you feel you need support, and you're always welcome here to vent and get additional support.