Ex Machina has some nudity, but less gun violence? It’s a lot more idea driven than action/violence driven (matrix). And the themes are different. Depends on what people culturally mean as adult I suppose.
I admittedly don't have kids, but media is so saturated and oversexualized that I personally feel that thought-provoking fiction that dissects and critiques urges is possible and good to explore at some point, in safe company, ammended with brief discussion. I'm certainly thankful I got offered these conversations.
That said, Ex Machina might be a little intense in that regard, even though I seem to remember that the explicity is mostly some nudity. It's a great movie, but probably not the first or fifth I would show a 12-year-old with the above discursive parameters included. The themes of corruption and "fucking around and finding out" are so heavy that you don't want to just leave a child with it.
It could be your tenth pick, though, or perhaps something for 6-18 months on of successfully watching and discussing movies and their depiction of life in an open way.