It would seem that this coming weekend is "Teach Your Kids to Game Weekend" and being that it is such a thing, Drivethrurpg.com is having a bit of a sale on some kid friendly games. Take a look if you get a minute, not just for any potential kids you may have but for the kid that still exists in all us gamers!
I've played Adventures in OZ, but by far my favorite on that list is +Justin Halliday's Hero Kids which a fun and very easy to pick up game. Seriously, I need to buy a new copy as I gave mine away to a brother and sisters trio at MEPAcon on Saturday after a very successful play through of "The Lost Village". Ages of these kids was 5-9 and even the youngest picked it up rather fast.
Now not everything is for sale, but there is a good bit and a mixture of free and pay-what-you want as well. Looking it over I am thinking of picking up (even though it isn't on sale and rather expensive) Little Wizards
as I've heard some good things about it around the web.