I am out of my depth with this, but I have been reading your posts. Wouldn't using the breathalyzer just humiliate her and provoke her. If she is going to lie, then she will lie test or no test.
I completely understand about not wanting her to drive with the kids if she has been drinking. If that is even an option right now, then maybe driving with the kids should be off the table.
Don't want to add to your confusion, but these two things really stand out to me.