Chrome allows for separate user accounts to be created, each with their own set of bookmarks and extensions. ‘Supervised user’ accounts can be created and managed to allow or prohibit access to certain websites, and create a log of browsing activity. A desktop icon can also be created for each user to provide easy access to their own Chrome settings.
To create additional user accounts, click on the Menu button then 'Settings' and click ‘Add new user…’ under the ‘Users’ heading.
Google Safe Search is enabled by default for supervised users and will filter Google search results. Restricting and filtering sites/services is a useful step as is having discussions with your child about what they do online and what to do if they ever see anything that worries/upsets them. Strategies could be as simple as turning off the screen, closing the laptop lid or walking away from the device then telling an adult.