Please note that the activity reported under 'Social Apps used' is not only the actual usage of an app on the device but can also be the social media websites your kids visited using a browser. Some websites and even some apps may have embedded Facebook, Twitter, Google+ pages etc... and they are reported under social app activities as well. Another scenario is if your kid has installed an app but haven't used it yet, reports may be shown for some apps due to the background activity of the app.
Our dev team is actively working on optimizing the reports related to social apps and the issue will be fixed in future updates. Meanwhile, you can check the 'Installed apps' in Activity tab and ensure the apps that are currently available/used on the device to keep an eye. Please bear with us and we will make sure the issue is resolved.