Is skyrim suitable for 12 year olds?

That depends largely on what you think the kids can handle.

Reasons against: The game is mainly combat-oriented, with sWords and shields and magic galore. There are several environments with blood in them, i.e. a dungeon floor with puddles of blood to show something dangerous is around. There is little swearing in the game, and there are one or two side missions with sexual innuendo. There is also a series of assassin quests, with some dark overtones to it.

Reasons for: Oblivion is pretty tame in comparison to most other games of the same nature, and surrounds the player in a very well-made fantasy environment. The game has a crime system that helps strongly discourage the player from just killing or stealing whatever they want, and even the "thieves guild" has penalties for killing innocents. Missions are layed out to present multiple solutions to a problem, encouraging the player to think things through before just plowing through all of the enemies. The enemies themselves are often magical creatures such as skeletons or overgrown insects.