Portal 2 is a phenomenal game. Its unique set of mechanics is a little mind boggling at first, but the game is very careful to make sure you're not in over your head and gives you a chance to get used to the portal mechanic.
The puzzles in this game are great, because they require you to think through the tools you're given and figure out how to apply them to the problem in front of you. However, some people might get frustrated if they get stuck and can't figure out what to do next. The puzzles are definitely not easy, but are very enjoyable for people who like a good challenge.
This game makes you think not only about how to solve the puzzles, but also bigger questions about the plot. The history of Aperture Science (the laboratory in which the game takes place) and different character's past lives is laid out in little breadcrumbs around the game, and it's up to the player to amalgamate all of these hints into their own theory about the game world.
Messages and role models: There are very little characters in Portal 2, and only one of them is a human (you.) However, each character has a distinct and interesting personality. GLaDOS, a murderous AI, is especially interesting because of the character development she goes through. Your own character can be a good role model for kids, because she never gives up. But she is a silent protagonist and never speaks, so doesn't have much of a personality.
Violence: Portal 2 doesn't have any blood or gore (unlike Portal 1, which did have some blood). There are Turrets which will shoot at and kill you, and near the end of the game, bombs are thrown at you. Your character can also be mashed by spiky plates or fall into bottomless pits and pits of a murky substance. When you die, it doesn't show your body. It just pauses at the point where you died so that you can analyze what you did wrong.
You don't commit much violence, only against robots (like disarming turrets by making them malfunction or redirecting bombs towards robots using your portal gun.) The antagonists throughout the game talk a lot about killing (you) but it's not that graphic.
There is no sex, drinking, drugs, or smoking. The worst word you will hear in this game is "hell."