The Wii version suffers from clunky, unrefined controls which make the game a real burden to play; and had the game not have had the Simpsons brand backing it up, then I probably wouldn't have bothered persisting with this game which was obviously rushed out in order to meet its deadline. I've also played the PS3 version, and the controls are only slightly improved over that of the Wii, however the poor controls seem to be universal across all platforms.
The DS version however, which was designed separately from its console brothers (even though the storyline and level locations are largely the same), is a side-scroller which plays a lot better than the meatier console versions. If you can, give the DS version a try as its technically, the most refined version of the lot.
Content wise, there is frequent hand-on-hand and projectile combat in The Simpsons Game, however the violence is cartoonish and is unlikely to cause concern (although some may be concerned by violence directed at child characters, which can be perpetrated by adult characters).
There is also some very mild language throughout the game which is unlikely to cause concern, and the game contains two uses of mild coarse language in the form of "b-tch", which is used in two cut-scenes in the console versions of the games, and just once in the DS version.
One level, which parodies the Grand Theft Auto series of games, features cat and mouse pimps and prostitutes, however, sexual innuendo is fairly minimal and is likely to fly over the heads of younger gamers.
The DS version is accessible for gamers of all ages, however, younger children may struggle with the flunky controls of the Wii/PS3/PS2/360/PSP versions. Worth a rental for casual Simpsons fans.