Sims usually isn't inappropriate. I have sims 3 on my iPod and the only "bad" thing is, once you get married, you can WooHoo with your partner. There's nothing bad, but if you call the romance bad, I don't think any Sims would be okay for your son. In every Sims game there is some kind of romance. Other than that, it's a very fun and addicting game!
Hope this helps!