Your children are 6 and 16 years old. When purchasing train tickets, if they are purchased online or through other methods, they usually need to enter their ID card information for verification. For 6-year-old children who have not yet applied for an ID card, they can use the ID number in the user’s registration book to purchase tickets. As for 16-year-old children, they can directly use their ID card information to purchase tickets. During the ticket purchase process, the system will automatically conduct verification of people and vehicles.