When a family travels to Canada together it is easy to assume only the adults need to sort out documents. An eTA, however, is issued per passport, not per family. Everyone travelling must be approved individually regardless of age, and the places where a child's application goes wrong are a little different from an adult's.
Infants need their own passport and their own eTA
A child is not covered by a parent's approval. Even a one-year-old must have a passport in their own name, and an eTA linked to that passport. If the child does not have a passport yet, obtaining one comes first; the application is made with the new passport number once it is issued.
A parent or guardian completes a minor's application
A parent or guardian may fill in the application on behalf of a minor. The form then includes the guardian's details, while the child's passport details must be entered exactly as printed in the child's passport. Entering a parent's passport data into a child's application is a surprisingly common slip, so complete one application at a time.
Start with the child's passport expiry date
An eTA lasts up to five years, but it ends on the passport expiry date if that comes first. Children's passports are often valid for a shorter period than adults', so check that the child's passport comfortably covers the trip before applying. If the passport would expire during the journey, a renewal comes first.
Family members with a different nationality may need a different document
If someone in the family holds a passport of a different nationality, their document requirement may differ: visa-exempt nationals use an eTA, while nationals who require a visa need a Visitor Visa. One person's document never extends to the others, so check each passport rather than judging the whole group by one.
Apply when you book the flights
Most applications are processed quickly, but when several are submitted at once, one of them may be sent for additional review and take days. Rather than applying for everyone just before departure, complete all the family's applications when the flights are booked, so a delay on one does not affect the plan. Confirm accommodation and local arrangements only after every approval has arrived.
Keep every approval email together
Collect all the family's approval emails in one place and, before departure, check that the passport number in each email matches that person's actual passport. The passport details in the flight bookings must belong to the same passports. Airlines verify the approval by passport at check-in, so a mismatch for one traveller can stop that person alone from boarding.
One eTA per traveller, children on their own passports, separate documents for different nationalities, and applications made when the flights are booked. Those four rules prevent almost every family-trip problem.