I do not really think that the Simpsons can be considered a cartoon for kids even if there are child characters. The characters are mature thinkers and there are also some signs of violence. Adults will get to enjoy this cartoon more than kids ever will.
There are some fun aspects of it that can be enjoyed by kids but as long as they do not reach a certain age yet, it is best viewed by teenagers who already know what is happening and adults who have loved the show since day 1. There are a lot of people who end up loving the Simpsons the more that they watch it.