Ocarina of Time 3D is a suitably epic quest that sees Link start off as a young boy, exploring the nooks and crannies of his forest home (which Miyamoto - the Zelda creator - apparently based on his own childhood, journeying through the caves and forests around his home), before heading off across the world of Hyrule, and even through time, as he tries to save Princess Zelda from Gannondorf, the ginger-haired Sorcerer.
While Link himself may be mute, everyone else in the land of Hyrule seems to do more than enough talking to make up for it, so very young players might not be able to manage too well, especially given a lot of directions on what to do next are mentioned in passing conversation.
Ocarina of Time 3D also features a series of hint videos, similar to those found in Mario Galaxy. At certain Sheikah Stones (tombstone looking things with an eye pattern on them), you can view hint movies of how to solve puzzles/progress through the game. It's certainly useful if you ever do get stuck, but there's only two Sheikah Stones in the game - One in Kokiri Forest, and another in the Temple of Time.
As a fantasy themed Nintendo adventure, there's little in the way of mature content in Zelda: Ocarina of Time. With no bad language, and no sex, perhaps the only thing we need to flag up is the game's very mild violence, whereby the game's hero, Link, can strike enemies with his sword, shoot them with his bow and arrows, or throw bombs at them. Suitably non-realistic in nature, most of the enemies you face off against aren't even slightly humanoid in nature, and what little blood there is in the game is usually blue or green, and tends to appear in bubbles from the enemy.