Is there a virtual world where you can create a 3D avatar without downloading for kids 8-12?

Ourworld is pretty awesome, but if you are specifically looking for 3D avatars then I suggest you check out Meez. I play it a lot and so do most of my friends and it's pretty cool.

Also if you like that you will also like games like The Sims I think. You can control a lot about their life and how they look, and hey even have kids and things like that, so yeah, sorry if that didn;t help