Have you told her, when you are sober, that you feel she is endangering your grandchildren?
God that would be so frustrating. I think i'd have a "come to Jesus" talk with her AND with her ex-husband about how this situation is affecting your grandchildren and your concerns regarding their safety.
and if that didn't work, I would seriously consider calling CPS or 9-1-1 the next time she is passed out drunk with little ones in the house.