Each of these sites has pertinent information to offer concerning internet safety for your children and how to implement some safeguards:
The links below can help you monitor and restrict your children's on-line activities or show you how to do so:
A Utility that allows you to view the browsing history for users on the computer: Nirsoft Browsing History Viewer
Setting up Restrictions on an iOS device (iPads, iPhones, iPods): iOS, Understanding Restrictions (Parental Controls)
Norton Internet Security Family Parental Controls: Norton Family
Symantec's Guides to Scary Internet Stuff
McAfee Parental Control set up information: McAfee Parental Controls
Setting up Parental Controls on a Windows Computer: Parental Controls on a Windows PC
Setting up Parental Controls on a MAC computer: Parental Controls on MAC