My first review! Here I go!
Personally, I think that this is one of if not the best anime out there. As for who it's appropriate for, you really just have to know you kids.
Violence: This anime is based off the manga of the same name. Since it is a shounen (Japanese for boy or young boy) anime/manga, there is going to be quite a bit of fighting and violence. Yes, there is quite a bit of blood, specifically in the fights that have Zoro (the swordsmen) as one of the participants. However, the violence is never without purpose. The main pirates, the Straw Hat Pirates, never just go out and pick fights with anyone they meet. There is always a reason. In fact, Luffy's role model told him that fighting isn't always the answer "You can pour booze on me. You can spit on me. You can punch me. I'll probably just laught that stuff off. But if you hurt a friend of mine...That is something I cannot forgive!"
Sexual Content: while there hasn't been much as of yet (Season 2, Fourth voyage coming soon as I type this) There will be a bit coming up. I know this because I watch the Japanese version and can tell which parts are going to be dubbed next. While the only thing that pops up is a bit of revealing clothing, in the Arabasta arc, there is a bath house scene. In Japan, bathing is a social event, but never do men and women bathe together. There is a separate section for each sex. A few hundred episodes later, there is the Amazon Lily Arc, where Luffy is sent to the Island of Women. Nothing happens, but that may be someting that parents will want to watch out for.
Language: In Japan, there aren't relaly any ways to curse. Instead, they just say things in a disrespectful manner. That doesn't have as much of an impact in America, so they add in a bit of language to convey the same meaning. Words such as @$$, h311, d@mn, and cr@p are used somewhat frequently. Sanji the chef uses cr@p/py fairly often (in Japan he says kuso which translates literally to excrement).
Product Placement: Absolutely none.
Drinking, Drugs, or Smoking: They are pirates, after all, so drinking is to be expected. Sanji does smoke quite a bit, and a few other characters smoke cigars, but that's it. In the Amazon Lily arc, Luffy eats a mushroom that turns out to be a special "Growing out of your body mushroom" that forces other mushrooms to grow out of his body, almost killing him. Remember kids, shrooms are bad for you!
Messages: Each arc has their own villain with their own set of bad values which are then stomped upon by Luffy and the rest of the Straw Hats. Example: Buggy says that gold, jewels, and other various shineys are the only kinds of treasure and that nothing else could ever be of value. Luffy's straw hat disagrees.
Role Models: Yes, Nami is a theif. We've established that. It is stressed that while her kleptomania has come in handy, it is the result of years of trying to pay back basically a mob boss to save her village. Kids don't have that problem. Usopp is a liar. The reason the Straw Hats have to fight so hard in the Captain Kuro arc is because of Usopp's lying, basically making it the boy who cried pirate.
Overall: One of the better animes out there. while there is quite a bit of violence, some language, and some tobacco and alcohol usage, the show in general is one of the best, especially if you like plot twists.