This game is rated 12+ by PEGI and there are many safety features, like most MMOG this game you can turn off the chat completely (recommended). The violence is stylized and you will never any human hitting another human. While with creatures there is occasional blood spray (can be turned off). The puzzles in it are quite interesting because you have a limited amount of flight time.
Overall: great game great graphics tweens and up!
I am 18 years old and a very responsible man and my take on this game is Its really great considering if your kids are 15+ I would not let a 13 or 14 year old play this game, because of the inappropriate things that are spoken in ingame chats. the sexuality is some what high but that's just like one forth of the game especially if you play as a male.
One serious draw back to any mmorpg is that if played to long it can cause serious social drawbacks to the user, so watch out for MMOs that your kids or teens play.