Every traveller needs their own ETA
There's no family or group application — each child, including babies, needs an individual UK ETA linked to their own passport.
Who applies on a child's behalf
A parent or legal guardian completes the application for anyone under 18.
Photo requirements for children
The same photo rules apply as for adults: recent, plain background, neutral expression — which can take a few tries with younger children.
Apply together to avoid mismatched travel dates
Submitting the whole family's applications around the same time helps keep everyone's approval status and validity dates aligned.