The royal wedding could provide a shot in the arm of more than £80m for the country’s slowing economy as retailers, pubs and hoteliers look to cash in on Harry and Meghan’s looming nuptials.

The tourist authority VisitBritain said about 50,000 Americans were expected to be among the crowds lining the roads in Windsor and soaking up the atmosphere in the capital when Prince Harry and Meghan Markle tie the knot later this month. Pubs have been given special permission to stay open late while retailers in London’s shopping district are anticipating a £60m mini sales boom on the back of tourist spending sprees.

“There could be a modest boost to GDP growth in the second quarter from the royal wedding and the football World Cup starting in mid-June,” said Howard Archer, chief economic adviser to economic forecasting group the EY Item Club. “There may well be a temporary boost to retail sales from people buying souvenirs and also to tourism.”

Airbnb said that with around 42,000 guest arrivals expected in London, hosts were set to rake in £12m from renting out their properties. In Windsor residents can earn £353 from the wedding weekend alone by using Airbnb to let their properties. The couple’s decision to get married in the grounds of Windsor Castle had also turned Slough, Maidenhead and Reading into rental hot spots, the company said.

With pub landlords given special permission to stay open until 1am on the eve of the nuptials, as well as on the day itself, the British Beer & Pub Association thinks the extended trading hours could deliver a £10m sales boost.

“Relaxed licensing hours for pubs will be welcomed by pub-goers and provide a real boost to the pub trade,” said Brigid Simmonds, chief executive of the BBPA – which represents the owners of 20,000 pubs.

The wedding clashes with the FA Cup final between Manchester United and Chelsea, but while the wedding kicks off at noon the action does not start at Wembley until teatime – avoiding potential tussles over the big screen.

Tim Martin, chair of JD Wetherspoon – which runs nearly 900 pubs, is less optimistic that the wedding will be good for business. “No disrespect to Harry and his missus but I can’t see the royal wedding moving the dial for the pub trade,” he said. “The public wish them all the best, but I feel the nuptials’ significance is overplayed.”

There is optimism that the good weather ushered in by the bank holiday will hang around for the next fortnight: 19 May is too far away for the Met Office to have honed its forecast, but it warns that “confidence for a continuing warm dry spell is low” on its website. Online gambling firm Betway is offering odds of 100/1 that the mercury will hit 100F (37.7C) on the big day.

The country’s beleaguered retailers have been limbering up for the event since the engagement was announced at the end of last year with merchandise running the gamut from twee £12 tea-towels at John Lewis to Argos’s £14.99 rip-off of Markle’s engagement ring in cubic zirconia rather than diamonds.

Markle has also been boosting the fortunes of British fashion retailers by mixing high street names such as Marks & Spencer and Jigsaw into her designer wardrobe for public engagements.

The big supermarkets are also expected to benefit as Britons host street parties and use the event as an excuse for a get-together. It is not clear how many street parties are taking place nationwide but the figure is likely to be in the hundreds, with Hertfordshire county council alone reporting 51 applications.

VisitBritain said the pomp and pageantry associated with the royal family was part of the country’s appeal to overseas visitors, with the bride’s nationality an added bonus because American visitors are the UK’s highest spending overseas group.

“We are looking at it as a showcasing moment on TV stations around the world,” said VisitBritain director Patricia Yates. “Our history and heritage is a huge draw internationally and this is an opportunity to reach a younger audience with a contemporary story.”