When you sign up to Habyts you automatically receive a free trial for 14 days. At the end of your 14 days you'll be given the option to sign up for a subscription.
We hope that you'll stay with us! If you decide not to continue, all previous Habyts controls will cease to work and your apps will no longer be available.
Therefore there is no need to cancel after the Free Trial.
You don’t need to uninstall the Habyts apps on your kids’ devices (though of course, you can do so if you want).
Please see: How do I remove Habyts from my Android device?