There is no limit to adding phones to your account. You can add as many children to your account. You don’t need to start from scratch and set up a whole new account, rather tap on the “+” sign on the upper right side of your FamilyTime - Dashboard. Now you can add a new contact, enter the user name, date of birth and your relation with user.
You will see the child account added to your account dashboard. But in order to start viewing reports and alerts from that child profile, you will have to download and install the FamilyTime app for children on their mobile devices.