Like most people have said here, I also think the way the game handless all the grown up stuff, like "woohoo" and "juice" is appropriate to a 10 year old. I mean, a kid that age probably knows something about that stuff already. And the way woohoo for example is shown in the game... Well, like people have already said, it doesn't really show anything. Just gives the idea the two (grown up) sims are having fun together.
Actually, a colleague of mine just told me she bought the game to her 10 year old son. Then, one day, they were coming home from somewhere and the boy was excited to get to playing, once back home, and said:"When we get home, I'm going to make a baby!" My friend wasn't shocked, she mostly found it funny, because, hey, it's just a game, not real life :)