You can restrict Pandora from playing songs or displaying ads with explicit content under the 'Settings’ section in the app:
 
If you are currently on the Now Playing screen touch the back arrow in the upper left (near the Pandora icon). Then select the Settings tab.
 
Next, select Account and uncheck the box next to ‘Allow Explicit Content.’ Make sure to hit ‘Save’ when you are finished.
 
Enabling this filter will limit Pandora to playing music that could play on daytime broadcast radio.  Note that this can only be applied to the entire account and NOT specific stations.  Once set, this will restrict explicit content for that account on all devices, as well.