Gregory and Moore, directors of landscaping firm Landform Consultants, have been in intensive training for the gruelling 26.2 mile race, being held on 25 April.
Moore explained: "We are asking you to dig deep and help us to raise as much as possible to ensure that the Children's Society's good works continue and grow.
As an extra incentive we are offering to put of anyone giving £25 or more into a draw to win a superb RHS Chelsea Flower Show experience."
The team - who are creating a show garden for the Children's Society at this year's RHS Chelsea Flower Show - are offering the following prizes.
1st Prize : Two day tickets, VIP treatment with champagne reception and a personal tour of the Children's Society garden designed by Mark Gregory and the ‘Spirit of Malaysia' garden designed by James Wong. Plus a signed copy of James Wong's book which accompanies his TV series, Grow Your Own Drugs.
2nd Prize: Two skilled gardeners (including equipment) for a whole day to work on your garden within a 50 mile radius of central London.
"You have nothing to lose and everything to gain," added Moore. "Even if it is just the feeling of helping out a great society and some very needy children."
Sponsor the team online at their Just Giving website.