Peter Phillips, the monarch's grandson whose entertainment firm is organising the extravaganza, said the not-for-profit event on June 12 will be called "Patron's Lunch" and have a "carnival atmosphere".
"There's a huge amount of pride, the fact that I'm able to celebrate, to put something on, to put a celebration on which ultimately she appreciates, she enjoys and she thinks is a great idea," said Phillips,the son of the Queen's daughter, Princess Anne, who came up with the idea as director of Sports Entertainment Ltd.
Most of the 10,000 guests will be from organisations associated with the Queen.
While a majority of the tickets have been pre-allocated, the firm will be able to sell 40 per cent of these through auctions or raffles, raising money to cover the cost of their other tickets or to go into charity funds.
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A ballot will open to the public in February for a minimum of 1,000 tickets, and winners will then be able to buy tickets from the event's website.
In total, the ticket sales will raise 1.5 million pounds towards the cost of the event, with any surplus donated to a new Patron's Fund to benefit various charities.
During the event, a carnival parade will travel through The Mall in central London to entertain the guests, and the Queen and Duke of Edinburgh will take to a stage to listen to speeches marking the occasion.
They will later join grandsons Prince William and Prince Harry, joint presidents of the event, in the royal box for part of the day.
The party will be the culmination of a weekend of UK-wide celebrations.
Other events taking place over the Queen's official birthday weekend will include a service of thanksgiving at St Paul's Cathedral and the traditional Trooping the Colour ceremony, also known as the Queen's Birthday Parade, at Horse Guards Parade in London.
The Patron's Lunch is intended to honour the Queen's lifetime service to the UK, as well as marking her patronage of more than 600 charities and organisations.