Sisters Hollie and Scarlett Page-Heyes will be having their long locks cut short to raise money for family friend Heather Bellamy.
Ms Bellamy, 48, of Downham Market, is battling acute myeloid leukaemia and needs to travel to America for treatment set to cost around £250,000.
Hollie, 12, and Scarlett, 6, will be the latest members of their family to raise money for Ms Bellamy, after their dad Chris Heyes walked more than 200 miles from Downham to Cardiff last month and raised more than £12,000.
Mum Louise Page, who has also raised money for the appeal through cake sales, said: “Heather was our family nurse and is a friend of ours.
“As a nurse she has looked after everyone else, now it’s our turn to look after her.”
With the money from the sponsored walk, cake sales and the girls’ haircuts, so far the family has raised more than £13,000.
Hollie and Scarlett will have their hair cut during the Downham Market Carnival on Monday.
They are set to have their hair cut in front of the crowds around 2pm in the arena on the Howdale.
Their hair will be donated to the Little Princess Trust, a charity providing free wigs to children who have lost their hair through cancer or other conditions.
There will also be a family fun day and charity football match for Ms Bellamy at Downham Market Academy on Sunday, July 28.
To help on the day, have a stall or donate a raffle prize, call Miss Page on 01366 383269 or 07944 781644.
To sponsor the girls, see uk.gofundme.com/little-and-large-go-short-and-sweet-for-heather