I would say: first of all - drop the word "confront" from your brainstorming about how to deal with your mom. Setting up "A Confrontation" probably would just stir up a bunch of anger. I know a lot of people think that "confront" means "taking a stand" and not allowing someone else to mistreat you. It's supposed to mean empowering yourself. In reality, it doesn't, IMO. That's just letting someone else "bait" you.

It may be that your mother is incapable of choosing to change her behavior. It is your behavior that has to change. When your mom holds up a hoop, you don't have to jump through it. When she says everyone has to start picking up crumbs, you don't have to comply. You need to practice "constructive disobedience." Ex: "No Mother, we're not going to pick up the crumbs right now. Those crumbs aren't bothering anyone and we're going to just forget about them at this time." Then do exactly that. Sit the kids down and explain that they have to be respectful of grandma, but that sometimes grandma has silly ideas and that you will let them know when a silly idea should not be paid attention to.

I know that will create a lot of tension, when you first try it. But the tension won't kill anyone. Stick with this approach and things may slowly change.

Grandma likes to make a big deal out of what is unimportant. Don't get baited into a big argument. Quiet refusal to take orders from grandma is the way you get yourself into a position of strength. Getting upset (and confrontational) with your mother allows her to win. Staying quiet, unperturbed and intent on ignoring her silly mandates is the way for you and the kids to escape her tyranny.