How to set up the Guest User account on your Mac
Open System Preferences.
Click on Users & Groups.
Click on the lock icon to unlock it, and enter your administrator name and password.
Click on Guest User and check the box marked Allow guests to log in to this computer.
You can also use the default Guest account on the mac, to enable after you unlock with admin passwords in system preferences.
Select Guest User in the accounts list and select “Allow guests to log in to this computer”.
You can use Parental controls to limit what they have access to further then defaults. Also keep in mind that when they log off any files they saved will be deleted.