Their father helped them sort through some of their belongings last month and set up the stall outside their home in St George’s Road, along with the tin for buyers to put money in.
The exercise was meant to teach the children a valuable lesson about managing their own money and saving enough to enjoy their day out.
However sometime between 16:00 and 16:20, a male was captured on CCTV taking the tin from the stall.
Guernsey Police are now investigating the incident and are asking that anyone with information get in touch on 725111, email jarrod.turian@guernsey.pnn.police.uk or call Crimestoppers anonymously on 0800 555 111.
Pictured top: Officers are looking to identify the man in the CCTV footage.