Sir Elton John, Arctic Monkeys and Robin Thicke are among the acts set to perform at the iTunes festival in September.
Stars from the world of music, film and sport joined Sir Elton John and David Furnish at the Elton John AIDS Foundation fundraiser.
Sir Elton John says he's worried about the difficult childhood facing his son as he battles homophobia and the impact of his father's fame.
Sir Elton John has cancelled a concert in the US tonight due to "medical reasons".
The star was scheduled to perform at the BJCC Arena in Birmingham, Alabama, but his publicist said the gig would not be going ahead.
They did not provide any further details as to what the medical reasons were.
Refunds will be available "at point of purchase" from Monday, the publicist added.
Sir Elton John has revealed he wants to have another baby - so his son has support when he is teased about not having a mother.
The pop superstar, 65, said he and partner David Furnish had talked about the prospect of Zachary being targeted over his untraditional family set-up before they fathered him with a surrogate mother 15 months ago.
In an interview with Guardian, Sir Elton said it was inevitable that the toddler would face pressure over his family life as he is growing up.
"I think it's difficult to be an only child, and to be an only child of someone famous," he said.
"I want him to have a sibling so he has someone to be with. I know when he goes to school there's going to be an awful lot of pressure, and I know he's going to have people saying, 'You don't have a mummy'.
"It's going to happen. We talked about it before we had him. I want someone to be at his side and back him up. We shall see."
The Rocket Man singer said the fact he was an only child of an unhappy marriage and spent a lot of time by himself listening to his parents argue was another reason why he wanted more children.
During the revealing interview, Sir Elton, who will perform at the Queen's Diamond Jubilee concert at Buckingham Palace tomorrow night, also revealed he worries about Zachary being spoilt by a global army-of well-wishers and friends.
He said: "At Christmas we bought him a swing for the garden and a little slide, and this was his Christmas present and his birthday present from us.
"But he had so many presents from other people throughout the world, which is touching, but we actually found it obscene."
The star, who has been know for his extravagant lifestyle, said they gave most of the gifts to charity.
Sir Elton John is "recovering" from a respiratory infection which resulted in him being admitted to hospital and cancelling three Las Vegas shows, his civil partner David Furnish has said.
Speaking at the Glamour Women Of The Year Awards, Furnish - who has a toddler, Zachary, with the singer - said: "Thank you for your well wishes. He's doing incredibly well and recovering."
Sir Elton John has cancelled three Las Vegas performances on doctors' orders after being taken to hospital with a respiratory infection.
Show officials say Sir Elton came down with the infection last weekend and was admitted to Cedars-Sinai Medical Centre on Wednesday.
Doctors have recommended he not perform for a week and take antibiotics. He was later released.
In a statement, the singer said that he is sorry he cannot be with his fans at The Colosseum.
– Sir Elton John
I'm so sad. This woman was the queen of disco and so much more.
That she has never been inducted into the Rock 'n' Roll Hall of Fame is a total disgrace especially when I see the second-rate talent that has been inducted.
Her records sound as good today as they ever did.
She is a great friend to me and to the Elton John AIDS Foundation and I will miss her greatly.