It was a great movie. I'm 12, and it was completely fine for me, but I'm not near as squeamish or anything as almost any kids my age. There was a lot of suspense and excitement, and a lot of violence. Most of it, not so bad, but my favorite scene was the one with the train crash. It seems to start as a carefree moment, they're filming a home-made zombie movie, and a train goes by. But, then, a pickup truck drives onto the tracks and right into the train. It seems a little overkill, I mean, how could a pickup truck make a 20-car-or-so train literally fall to pieces? But, in theaters, the sounds with screeching and explosions literally had me holding my breath throughout the crash, to the end when pieces were falling from the sky. So, as I said earlier that I'm better handling this than most kids my age, you might want to comfort your children around this scene ages 10-12, or maybe you may wait until it comes out on DVD. But, as always, I don't know your children as good as you do, so it's on a case-by-case basis.
I didn't have language as an issue. Most of you parents may not know, but children in late elementary school, and especially middle school, seem to curse a lot more than you think. In 6th grade, I honestly hear worse than what was in this movie, in just half an hour at school. But, if you think it's different, so be it. They loosely used d*ck, a**, a**hole, dumba**, sh*t, d*mn, and h*ll. Almost only, actually, in carefree moments, when you'd expect they'd use those before throwing up when in real danger, but they didn't at all. However, one kid did throw up twice. They also used f*ck once, Which I will explain with drugs.
There's a lot of smoking in the movie, but other than that, just about all the drugs were consumed by an older teenager that worked at the camera shop. He tried to sell the kids marijuana, and then was high so he couldn't drive, so one of the ~12-13 year olds drove. He then used their f*ck word while he was high, when in my opinion, they should've used it after the train crash, or in a scene where the main character was having an intense argument with his dad.
So, it was a great movie, especially with suspense, but the major things were the train crash scene, someone smoking marijuana, and a single use of the F word.