Apologies it seems there are different rules for departure and arrival e-gates. I'm guessing your kids were deemed old enough to follow the instructions.
On
departure, use of SmartGates requires the user to:
- have a machine readable passport
- be able to follow the instructions (i.e. not babies, small children or people who need assistance)
- not be a domestic traveller on an international flight
On
arrival, use of SmartGates requires the user to:
- have an ePassport symbol on your passport
- be at least 1.1m tall
- be least seven years of age and travelling with a parent or legal guardian
- not be a domestic traveller on an international flight
- not be an unaccompanied child under 16 years of age