I started playing the original Sims when I was about seven years old. I thought the game was very fun and stayed with the series as it grew into Sims three. My sister a teen at the time used to play and I always bugged her about playing until my parents bought me a copy. I know the rating said I needed to be older but to me it was a safe way to interact with something and still have fun. You can control the lives of your Sims by getting Jobs, choosing how your family lives and having your children and teens go to school. To me the only naughty things are making babies, but even then you can't see anything other than your Sims going under the sheets and the sheets moving. So to me if I had kids, it would be okay to me. And you can get into fights in the game, some parents are not okay with their kids seeing any type of violence, and that's okay. But I feel the need to add that all you can really see is a ball of smoke and various body parts poking out of the smoke until the fight ends and someone wins. The game will show you being able to do other actions though such as shove and other actions as well as a verity of insults I can't remember all of them since I rarely ever use mean interactions. In this game you can have friends, enemies, lovers and the best part of it to me is the family tree. I adore seeing how my family has grown and expanded through my time of playing.
In my opinion I would let a child at least the age of ten play. I couldn't see my seven year old nephew play it and not just giggle at the baby making aspect. Some children take the reality of life more seriously than others so I guess it would very per child as well as what parents want their children to view and play.
This is just my opinion. I do suggest doing some research on the game before buying it for kids, to see if you really think its okay for them. I know even as an adult I do the same for games I buy my nieces and nephews, just to make sure it really is what I think is age appropriate.