November 1, 2010
You can manage what children have access to in the iTunes Store by using the Parental tab in the iTunes Preferences panel (available via the iTunes menu on the Mac and the Edit menu in Windows). Select Parental to see a set of content restriction options for movies, TV shows, and apps that can be tuned (G, PG, PG-13, and more) and checked on and off. When you set Movies to PG-13, for instance, the purchase and trailer buttons for movies rated R will be inactive as well. Plus, you have the option to restrict all content identified as explicit. You can also disable access to the iTunes Store altogether as well as Podcasts, Radio, and Shared Libraries.
When you make changes to the settings, be sure to click the lock in the lower left of the panel before leaving it to ensure they can't changed again without your password.