Kevin Wright bowed his head in the dock as a jury of seven women and five men found him guilty of 10 counts of theft and two of fraud after a trial lasting more than five weeks.
Wright stole a total of £171,500 from the Bobby Wright Cancer Fighting Fund, including donations of £60,000 made by charities Caudwell Children and Janet Nash.
He set up the fund to raise money for treatment for his son Bobby after he was diagnosed with neuroblastoma - a rare form of cancer - at the age of three in 2005.
Wright, 49, from Quince, Amington, Staffordshire, also stole cash and credit balances from appeals he set up to raise money for cancer treatment for youngsters Callum Kaye, aged three, and Armani Mohammad, also aged three.
The money went into Wright's personal bank account to fund his "interests, investments and personal lifestyle", the court heard.
Jurors heard Wright, formerly of Kenn near Exeter, gave £20,000 to a friend who ran a used-car business and that he put £60,000 into Premium Bonds.
Wright claimed the restaurant and pub ventures were aimed at promoting natural food and were part of the fundraising, with any profits going back into the appeal funds.
Asked why any promotional material did not mention cancer, Wright told the court: "Who would want to go and eat in a cancer-themed restaurant?
"It's not going to pull people in, it's going to drive them away."
Wright set up a number of appeals for other children with cancer. He advised their parents to feed their child an organic diet as this had helped his son Bobby to overcome cancer.
The mother of one child who was diagnosed with a brain tumour wept as she told the court she was never made aware of the amount Wright raised for her son.
Wright set up Callum's Appeal to raise money for treatment for Callum Kaye, who was diagnosed with a brain tumour in 2005.
Giving evidence, Callum's mother Anna Kaye told jurors Mr Wright gave her advice about organic food and supplements and told her about life-saving treatment at a US hospital.
However when they visited the hospital, doctors said the treatment was not appropriate for Callum.
Following the trip in December 2008, she told Wright she no longer felt comfortable fundraising for her son as he wasn't going to be treated in the US.
But she told the court Mr Wright told her they should "keep going until the end of the year".
Giving evidence in his defence, Wright told the jury that every penny he raised was intended to help youngsters living with cancer.
After Bobby, who is now aged 11 and cancer-free, responded well to a variety of holistic and natural therapies, he said he wanted to help others in a similar situation.
Wright was found guilty of 10 counts of theft and two of fraud by false representation. He was cleared of one count of fraud by false representation.
Following the verdicts, Judge Greg Dickinson told the court Wright had two previous convictions for theft and another for forgery.
Wright will be sentenced at Nottingham Crown Court on September 5.