Last weekend SIL had a big night out with friends (normal for her) she was really drunk and threw up. She popped round to our house the next day with the 2 children (under 5) after approximately 6-8 hours sleep, she still seemed pretty out of it (basically passed out on the sofa at one point) she complained that she still felt sick and dizzy. After 2 hours she finally left with her 2 children and drove home, i was sick with worry but they were ok. After a long discussion with dm i knew i should have reported her at the time. I have tried to discuss this with db but he doesn't seem to care (i did tell him that its not only her kids in the car with her its the innocent family going about their daily life that she may seriously injure) i was told that i was being stupid and that i should mind my own business 
i live in scotland the drink driving laws have changed and are different from the rest of the uk, she would've still been way over the limit the next day. Would it be U to report her? Not only to the police but social services aswell? I don't want them to lose their children but i think she needs some help.