Children aged 10 and 11 will be able to use passport e-gates at the UK border from Monday, after the government announced a change to the rules.
Currently, only eligible children aged 12 and above can use the e-gates, which are at 15 air and rail ports.
The change comes after successful trials at Gatwick, Stansted and Heathrow, the government said.
It comes as families embarking on summer holiday getaways were hit by traffic jams and delays on Friday.
Passenger volumes are expected to return to 2019 levels this summer - with some ports exceeding those volumes, the government said. Border Force expects to see over 34 million air arrivals coming through UK passport control over the coming months, it added.
More than 400,000 children aged 10 and 11 are expected to use e-gates this year.
The gates are installed at 13 airports in the UK - Heathrow, Gatwick, Stansted, London City, Luton, Birmingham, Bristol, Cardiff, East Midlands, Edinburgh, Glasgow, Manchester and Newcastle. They are also in use at the UK border controls at the Eurostar terminals in Brussels and Paris.
Immigration Minister Robert Jenrick said the rollout "will make travelling easier for passengers and strengthens the security of the UK border."
"The UK processes more passengers through e-gates than any other country - and today's announcement ensures we remain at the forefront of technology," he added.
But the e-gate service has run into difficulties in the past, with airports across England and Scotland caught in lengthy queues when the gates stopped working at the end of May.
The disruption, which lasted for over a day, was caused by an IT issue, the Home Office told the BBC. It saw travellers waiting in long queues for hours.
On Friday, the Port of Dover said it had been a "popular day" with travellers heading to France. Earlier it had warned holidaymakers to expect delays to pass border controls, with processing times given of up to 90 minutes.
Families were also hit by traffic jams and delays at the Dartford Crossing.
National Highways closed part of the River Thames crossing because of a crash on Friday, causing long tailbacks.
The smash forced the closure of one of the crossing's two tunnels, which are used for northbound traffic, shortly before 07:00 BST.
The tunnel was later reopened but National Highways said the incident caused five miles of congestion.
An estimated 12.6 million car journeys will be made for a day trip or holiday between Friday and Monday as the majority of schools in England and Wales finish for the summer, the RAC said.
Earlier this week, the first passports were issued in King Charles's name.
Passports will now use the wording "His Majesty", with the era finally ending for passports using "Her Majesty", for the late Queen Elizabeth II.
The updated passports are the latest stage in the gradual transition in reigns, with stamps and some coins now carrying the King's head. Banknotes will begin to change next year.