As a longtime player of WolfQuest, I can safely say that this game is a great educational option. I rated it for 8+, but really it depends on the individual child. I was 9 when I started playing, but I doubt it would have had a negative impact on me had I played it when I was younger. For those who are very concerned about violence, it should be noted that the game does depict the life of a real wolf, which is not always peaceful and, as wolves are carnivores, often involves violence (hunting). In WolfQuest, players must hunt for food and occasionally fend off predators. Interactions with other wolves may not always go well either, and players might have to fight then, too. These fights are not at all bloody, however, and compared to many games on the market today, the violence is very minimal. In the second mission, the player can go to a cattle ranch and kill and eat a calf. Failing this mission results in the player getting shot, however this is bloodless and only results in a loud sound effect and instant death of the player's wolf. Animal carcasses do appear (and serve as the player's food source), and these do show some blood/skeletons. However, it isn't very graphic. This is where the age rating might not be hard and fast- some people are more sensitive to that than others.
There's not much sexual content to speak of. The player does have to look for and find a mate, but nothing is shown beyond typical canine greetings- nothing worse than the affection you might get from the family dog. In the second episode, the player raises and cares for puppies-- again, nothing is shown or explained.
Probably the biggest concern with WolfQuest is the multiplayer environment. In the paid version of the 2.7 update, the player can enter multiplayer and interact and chat with other players. I haven't seen nearly as many incidences of inappropriate behavior in the 2.7 update than I used to in the earlier versions (it's now impossible to access multiplayer in 2.5, so this is no longer a concern for that version). However, that's not to say that it doesn't exist at all. I know the developers are extremely committed to keeping WolfQuest as safe and appropriate as possible, and they've been doing a wonderful job so far. As with any online interaction, however, multiplayer interactions are not guaranteed to be completely safe. If this is a concern, certain games may have only "phrase chat", where the player can select from a list of prexisting options. These games are generally safer than normal chat (which uses a blacklist to filter out certain words). There are also private games, which only those who have the game's username and password can enter. If your child has a group of friends who play the game, this can be utilized to keep strangers from joining. In the open chat, cursing and inappropriate words are filtered, however if someone is determined enough, they can find ways to cheat the filter.
All in all, WolfQuest is a safe, family friendly game that anyone can enjoy. There is minimal violence, and almost no blood. There's virtually no sexual content, and no language in the singleplayer game. Multiplayer is available in the paid version of 2.7, and while most multiplayer interactions are positive and child friendly, as with any online game it is not a guarantee. However, WolfQuest multiplayer games are generally more child-safe than the average open Minecraft server. I would highly recommend this game to anyone who likes animals and nature. As far as animal sim games go, WolfQuest is pretty much the best there is.