Your MIL seems to need to be told that she is not the parent of your children. Unless there's literal abuse and neglect, have a backbone for your parenting and don't get walked over. I'll only hear constructive criticism from my parents/in-laws away from my kids and way after the event takes place so we both have cool heads about it.

sic your son on her

Tell her to fuck off. How you raise your kids is your business and no one else's. Tell her to call CPS if she wants them to come out to investigate a feelings-hurting.

What about the younger BROTHER's feelings AND physical discomfort? Tell your MIL to mind her OWN business, not yours....

tell her to fuck off she isn't his mother

Unless your MIL has custody of your kids. She has no right to yell at you. You did the right thing end of story. If she keeps it up then she doesn’t have to see her grandkids anymore

Ask your mother in law if she would appreciate being picked up by her throat 🤷🏻‍♀️