He sponsors five children in India and Tanzania, and has travelled to meet them. On one trip, after meeting a sponsored child with a club foot, he paid for her to have corrective surgery.
Mr Grantham has also shared his story of selling chocolate to make a difference at schools, community groups and churches, and given presentations at seminars and conferences in New Zealand, Australia, the Cook Islands and Hawaii.
And he continues to sell to shoppers every Saturday in Broadway, opposite Westfield 277.
Mr Grantham's father, Chris Grantham, said his son sold every day in the lead-up to Christmas Day, although he usually took a break after Easter - "there's no point trying to sell chocolates for at least a week".
Over the years, Mark Grantham has had a number of high-profile customers, including rugby star Michael Jones and former Auckland mayors John Banks and Dick Hubbard.
Former Prime Minister Dame Jenny Shipley also often stopped for a chat, Mr Grantham said.
His efforts have also seen him named Newmarket volunteer of the year, and win the Spirit award in the 2011 Attitude awards, for someone who overcomes hardship to achieve their goals.
Queen's Service Medal, for services to the community.