Titled 'the magnificent seven' by the charity, the group are taking on challenges including walking all the way around the world, running a marathon on the Great Wall of China, climbing to Everest Base camp, and cycling around the island of Mallorca.
Funds raised through their efforts will support the Puzzle Centre, which helps children and families struggling with the challenges of autism – and aims to set up a national centre for excellence in Milton Keynes.
The most adventurous of all the expeditions is being undertaken by Swanbourne based author and adventurer Tom Fremantle, who is aiming to circumnavigate the globe on foot.
Tom, who has previously cycled to Australia, is carrying his belongings in a small cart and walking 20 miles a day.
His 16,300-mile, three-and-a-half year journey will take him from the US-Mexican border, across Europe, Africa, Australasia and Asia.
He is aiming to raise £30,000, to be shared between the Puzzle Centre and two other charities.
Tom said: “Walking around the world sounds bonkers but it is actually quite doable.
"I love walking and most of us do not walk nearly enough.
"During this walk, I hope to show that we can trust each other more and fear each other less.”
In the coming weeks his trek brings him to the UK, where he will be inviting people to join him on a 26-mile companion walk.
The second fundraiser of the 'magnificent seven' is Winslow Rotary Club member Don James who is currently climbing to the Everest base camp in Nepal, with the aim of raising £5,000 to support the Puzzle Centre.
Funds raised from his walk will be used to train teachers and therapists in PACT – an autism communication therapy for pre-school children.
On his return Don will be giving a talk to the Winslow Rotarians on June 4 when there will also be a cheque presentation to the Puzzle Centre.
Speaking before his departure he said: “I am going to trek to the most iconic base camp of all, at the foot of the greatest mountain in the world.
"This is one of the world's classic treks of 84 miles to the base camp and back.”
The third fundraiser is travel blogger Jordan Simons, a former pupil at Buckingham’s Royal Latin School, who will be battling gravity when he competes in the Jin Shan Ling Great Wall Marathon in China on April 21.
The 26-mile run will see him climb more than 6,000 feet in temperatures up to 24C.
Jordan quit his job and sold his belongings in 2014 and has spent four years visiting more than 60 countries and running a global travel blog from his laptop.
He said: “I grew up in Buckingham and even though I travel a lot now, it will always be my home.
"I was fortunate to have a good education that has enabled me to do the things I am passionate about – I believe everyone should have that chance, which Puzzle are providing to young children with autism and other communications difficulties.
“I’ve never run a marathon before – or even a half marathon – and this will definitely be the biggest challenge of my life so far.”
A week later on April 27, the fourth fundraiser, Puzzle Centre friend Lee Burgess, will cycle around the Spanish island of Mallorca – a total of 194 miles – in a single day.
Lee, who currently lives in Cumbria and aims to raise £1,000, said: “The support and care which the Puzzle Centre gives to families has an immense positive impact on understanding the development needs of the children and on quality of life for the whole family.”
Closer to home, the next featured fundraisers, Puzzle Centre trustee Guy Brogden and his son Archie will be running the Milton Keynes Marathon on Monday May 6.
And completing the 'magnificent seven' on June 15 will be Christian Dixon from Brackley, head of partner management at Mercedes-Benz Formula E team, who will be running his first ultra marathon, 69 miles along Hadrian’s Wall from Carlisle to Newcastle.
He said: “Apart from the run itself, this event will be a huge challenge as I expect to accumulate over 1,000km in training and dedicate over 100 hours.
"The Puzzle Centre’s support positively impacts so many lives and I hope that we can make a positive impact as well.”