Mrs Brown, wife of former prime minister Gordon Brown, will attempt the Fife coastal path along with Great British Bake Off presenter Sandi Toksvig and her wife Debbie, actress Arabella Weir and author Kathy Lette.
The five have already begun training for the five-day hike which stretches from Kincardine to Newburgh.
They are due to set off on July 30 with special events planned along the route including at North Queensferry, Aberdour and Kirkcaldy.
All of the money raised will go to Mrs Brown’s charity Theirworld, which works to bring better health and education to the world’s most vulnerable children.
Mrs Brown said the five were “a tiny bit apprehensive but hugely excited” ahead of the walk.
She said: “Theirworld works in the UK and around the world with projects ranging from code clubs for girls in Africa, teacher training programmes in Turkey for Syrian refugee children and school nutrition programmes and tech clubs in Lebanon.”
She urged people to turn up and support the walkers as they pass through towns and villages along the route.