Be careful about violent video games and kids. Violent games like the ones used in the study below (Carmageddon, Duke Nukem, MOrtal Kombat, Future Cop) physiologically desensitized players when they they were presented with scenes of real-life violence.
Video game violence also seems to have more powerful effects on children than movie violence - maybe because with video games, they interact with the images more directly. It's a spooky thing, too, that violent television exposure at an early age appears to have a greater effect on later violent behavior than low IQ, abusive parents, exposure to antisocial peers, or a broken home.
Desensitization to Scenes of Real-Life Violence with Violent Video Game Play
Video Game Violence Worse Than Movie Violence for Kids Press Release
Video Game Violence pdf