I've never actually played any of the GTA games so I may be totally wrong and feel free to point it out if I am, but isn't the singleplayer experience mostly "hey there's a story but ey who gives a forget if you get bored just pick up some guns and start shooting stuff"
To me, that's what the Grand Theft Auto series is, just a giant richard-around sandbox of fun.
Really, if you are a parent, you really should not buy your immature child a game like Grand Theft Auto. If your child
understands the difference between a video game and real life, you could let them play violent games. I was allowed to play Halo/Halo 2 back in like kindergarten or first grade. My parents understood that I knew the difference and it was just aliens in a virtual world.