George and Charlotte have attended high-profile events before, while Louis was considered too young.
The children delighted crowds during the Queen's Platinum Jubilee celebrations with their royal waves and playful antics.
Changes to King Charles' Coronation are expected, with a smaller guest list and a shorter ceremony.
The previous coronation had a grand procession with over 40,000 UK and Commonwealth service personnel.
The late Queen's coronation was the last time ten Commonwealth prime ministers travelled in open-top carriages.
The royal children will play a key role in their grandfather's upcoming Coronation on May 6.