A classic, but watch it with your kid and skip one scene
My kids, 9 and 10 ask me all the time what my favorite movies are and the first two Terminator movies are always listed. I had always figured I would have to wait until my kids were in high school to share these movies with them, but one of my friends said, "There's one sex scene, skip that and it's really not that bad..."
His point was a good one. There is bad language in the movie, but it's not over the top. I always tell my kids, "You can never completely avoid bad language, you just have to know not to repeat it."
My 10-year-old loved the movie. I fast-forwarded through the sex scene, but I let him know what had happened since it's kind of a key plot point for the series going forward.
The ultimate reason I wanted my kids to see this movie, aside from wanting to watch something with them that wasn't animated, was to teach them about heroes. There isn't enough of that with most of the movies that have come out recently and I liked the idea of them seeing Kyle Riggs and realizing that he gave his life (spoiler alert) to protect Sarah Connor from the Terminator.
He had the reaction that I wanted him to have to the movie.
I think if you watch this with your kids and interject where needed or explain certain things, this movie is fine for kids in the 10-12 age range as long as you skip the one sex scene. It didn't even interrupt the movie, I just tapped FF twice and we were past it.