I have done it. GM'ed "No Thank you, Evil" for my daughters 7 year old birthday party. She requested it, we've played before. Went great.

I'm still entranced by how kids do not view most encounters as near-automatic combat. That's definitely a learned behavior. (Also they all want to share their ideas, preferably by shouting). Anyway, they got the King and Queen's treasure back by helping the evil ogre (who stole the treasure) clean his stinky, trash-filled castle. #KidRPGs #nothankyouevil