This being my favorite game of all time, I had to review it.
I'll first say this: if you play the single-player portion of the game, I strongly suggest you play the original StarCraft and its expansion pack, StarCraft: Brood War, or look up the events that took place in them.
Moving on, the game can get very violent, with a lot of (not-too-realistic) blood, shootings, and frightening imagery.
When you shoot humans (Terrans) and the aliens (Zerg), there is some blood, but it's not realistic, and it's not excessive. I'm not sure if there is blood when you attack the third race featured in the game (the Protoss), but if it's anything like the first game, they either vanish in a puff of blue smoke or spew blue-colored ooze.
The Zerg will look incredibly frightening to younger kids, especially Kerrigan (also known as The Queen of Blades).
There is also a fair amount of cursing in the game, but it's nothing you wouldn't hear in an episode of The Simpsons, or even a PG movie.
The characters drink and smoke, but in my opinion, this is the thing to worry the least about.
There is one suggestive thing in this game, and it's that one of the main characters has a tattoo of a woman lifting her skirt up on his armor (but nothing explicit is shown).
Surprisingly, through a field of violence and cursing, the game is educational. Players have to carefully devise stratedgies for each level, and it takes quite a bit of concentration, thinking, and creativity.
The main character, Jim Raynor, can be a good role model, as he never gives up on his goals, dreams, and is always willing to help those in need.
Also, the game's controls are VERY easy to master, as their are several tutorials and videos to learn from.
I strongly recommend this game; it'll keep you playing for a long time, because there are a lot of missions, features, and a multi-player online mode that always holds something new and fun for players.