I am using Stack Overflow since last years, every thing about programming and life is there, but I did not found any thing for kids.
Some thing for kids should be here.
Stack Exchange (and Area 51, in particular) is a community-driven process. If your area of expertise doesn't already have a Stack Exchange site, propose it here. If there is an enthusiastic, committed group of expert users who will use the site, we create it. Before someone takes the initiative to propose and evangelize a site idea, there is no site.
But regarding a Stack Exchange site specifically targeted at children: Our Terms of Service does not allow for use of our services by children under the age of 13. That's mostly due to the restrictions regarding collecting information from minors and what they can be exposed to online.