It is required to use a unique email address when personalising each ticket. Fortunately, you can easily solve this: you can enter your own email address and add your child's name behind it. For example, your child’s name is Frank, then you can enter your email as : address+frank@gmail.com. As the main buyer, you will still receive all tickets and an incorrect email address has no effect on the medal for the children, as they will also receive this without entering a valid email address.