The Government is planning a lottery through which members of the public will win tickets to the extravaganza, enabling ministers to present it as a "people's party".
But the decision by the Queen and Prince Philip to take part in the high- profile launch of the Greenwich exhibition, despite reports that they were intending to boycott the event and that Prince Charles dislikes the Dome, will be a huge boost to the party.
Champagne will be served all night as stars perform for the expected 10,000 guests at the Dome on 31 December.
Prince Charles and other senior royals have not yet decided how to celebrate the new year. However, Princes William and Harry are likely to be given a private tour of the Dome in advance of the opening, as the New Millennium Experience Company, organising the exhibition, is keen to highlight its appeal to children.
Members of the Royal Family also intend to spend time in different parts of the United Kingdom during the four-day millennium weekend. It is thought they will split up and attend church services in the capitals of England, Scotland Wales and Northern Ireland on the Sunday, to prove their commitment to the Union.
The Government will announce this week that an additional pounds 5m of lottery money will be set aside to pay for events in the first weekend of 2000. All Britain's cities, towns and villages will be eligible for grants to subsidise their celebrations.
Chris Smith, Culture Secretary, wants the millennium weekend to have a lasting impact. "Resources will be made available to ensure that celebrations can take place across the UK during the first weekend of 2000," he said.