Carnage shows a very real slice of life where kids are usually told to "leave the room while we fight about you".
Our policy for raising our kids has always been to expose them to what is reasonable without them getting hurt. So just because Aunt Lindsay has a potty mouth doesn't mean we don't hang out with Aunt Lindsay. This movie has a lot of swearing—but no more than what happens in a real-life adult serious disagreement. There is also drinking.
The movie shows a very real slice of life where kids are usually told to "leave the room while we fight about you". Because this was not actually about our kids, friends, or family but rather just a movie, it gave our kids a minute to explore the very real emotions of adults. My 10-year-old has the attention span of a puppy, and she was riveted to the screen. Same thing for our 13-year-old.
All of these parents were heroes. For two hours they fought for their children. They came to the encounter as flawed humans doing the best they know how.
My 13 year old made the comment, "Oh this is like "The Breakfast Club" only with adults". She's right. By contrast, we have resisted her watching Breakfast Club (and she maintains that she has not actually seen it). I felt this movie was acceptable.
If your kids occasionally get to see their parents drink, maybe get a little drunk, and once in awhile get into a passionate argument, then you should watch this with them. If you live in a make-believe world where this doesn't exist, then maybe not.