The sporting heroes will be helping Wishaw shoppers at the checkouts in support of the Sue Ryder Foundation and the Les Hoey Christmas party.
Charlie, 20, was a star at the Commonwealth Games after winning gold in the men's lightweight boxing and will be joining Glasgow star Willie Limond on Saturday.
Willie currently holds the British and Commonwealth light-welterweight titles, and will be helping to pack shopping bags with his boxing companion.
Taking place at Morrisons in Kirk Road, Wishaw, families can enjoy a host of activities during the fun day including face-painting and a tombola.
Organiser Les Hoey hopes the fundraiser will raise at least £1000 for the two charities which both help people with life-limiting illnesses.
He said: "Charlie and Willie are going to bring their belts down and will be getting pictures taken with families as well.
"Some of the kids will be there and we've got about 20 volunteers helping out each day."
The charity superstar was given an MBE after spending more than a decade helping unwell youngsters.
Earlier this week he took hordes of children to see Ant 'n' Dec where they got to meet the stars.