The National Crime Agency said Jo-Emma Larvin, Jonathan Johnson, Beatrice Auty and Amy Harrison were part of a scheme which saw more than £104m leave the UK.
The cash was moved via Heathrow in 83 trips between 2019-2020, officers said.
The four were convicted of removing cash which they knew or suspected was the result of criminal activity.
On Tuesday at Isleworth Crown Court, fifth defendant Liam Rabone, 29, from West Kensington, London, was cleared of the charge.
The trial previously heard the defendants would travel business class to allow for extra luggage, with a letter from a company called Omnivest given to customs in Dubai while the cash was declared.