I am on the side involved with an organization that does similar charity flights. I know that they budget 100 euros for each flight. This is for a flight duration of about 30-40 minutes, which is about the point where the novelty wears off for a typical child.
According to the article his charity has been operating since 1998, has 60.000 UKP running costs per year, and has flown about 500 children so far.
That's over a 1000 UKP per child. Something doesn't add up.