First of all, the game is totally not iffy for 13 year olds. When I finally turned 13 and my dad let me play it my first thought was 'wow I waited a year or two to play this'
It's completely cartoony, the tanks go 'pwoosh' when they shoot, not realistic noises. Absolutely no blood, the bullets just bounce off of you and inflict damage. Ten year olds can play this. The only reason it may have some higher rating on it is probably because that's what the other battlefield games have and they didn't want to bother having ESRB review this or something.
As for the quality of the game, I was very disappointed. I was all excited about being a commando, the knifer/sniper who can go invisible until they get too close or attack. If you want to be a sniper, go see other games. A headshot will take away less than half of their health (this is with a sniper rifle!) and to prevent 'overpowering' the sniper rifles the closer they are the less damage they do, and the scopes on them are terrible. The game has a TON of consumerism. A common consumerism tactic is to sell a parallel currency that gets you special things and can only be bought with real money. In this game it is Battlefunds. Not only do you need battlefunds to customize your guy, but also if you want to buy a weapon for more than 3 days. I used to be somewhat okay with this, because Battlefunds couldn't give you an in-game advantage, but now they can. Battlefield Heroes now sells better assault rifles like the m16(an anachronism in this WWII game) and better sniper rifles (which STILL can't do instant headshot kills) and better machine guns. At this point just pay 10 dollars for the Battlefield deluxe pack and you will get several better games and nobody will be able to buy an advantage over you. Lastly, there is no chat filter, though SOME servers will kick you for bad language. I've only seen one or two such servers, and in one of them I got kicked for saying 'gg' or 'good game' at the end. Save yourself the frustration and disappointment and seek elsewhere for shooters.