"We are confident that there will be huge demonstrations against Trump wherever he visits", said Chris Nineham, of the Stop the War Coalition, which is helping to stage the so-called "carnival of protest".
American and British officials insisted his programme had not been deliberately arranged to avoid protest areas.
The visit, the first of its kind since Trump assumed presidency in January previous year, was categorized by the U.S. State Department as a "working visit".
During the dinner, the Countess of Wessex's Orchestra will perform a series of classic British and American hits.
The president will spend Thursday night at US Ambassador Robert "Woody" Johnson's London residence but will otherwise steer clear of the city.
A petition calling for the invite to be rescinded garnered more than 1.8 million signatures, forcing parliament into a debate and the government to issue a statement stating that "the President of the United States should be extended the full courtesy of a State Visit".
Mr Trump, whose mother was Scottish, will then be piped out at the end by the Royal Regiment of Scotland.
Leo Murray, one of the protest organizers, told Sky News: "Following a huge groundswell of public support for our plan, it looks like City Hall has rediscovered its sense of humor".
But, Murray added, Khan's administration had eventually "rediscovered its sense of humour - Trump Baby will fly".
However, the U.S. ambassador to the UK, Woody Johnson, has refuted such ideas.
Trump's exposure to London will be mostly limited to Winfield House, the USA ambassador's residence in Regent's Park. Afterwards - in what could be the most politically tricky part of the visit for Trump - the pair will hold a joint press conference.
That will be about the extent of Trump's exposure to London.
Trump will be kept away from the streets of London as part of a carefully orchestrated schedule created to shield him from demonstrations.
Britain regards its close ties with the United States, which it refers to as the special relationship, as a pillar of its foreign and trading policy as it prepares to leave the European Union. "The President is merely trying to get as impactful a trip as he can get in a 24-hour period", CNN reported.
On Friday morning, Trump will join May at a still-undisclosed site to observe "cutting edge military capabilities and integrated UK-US military training".
The US President also sparked a backlash from author JK Rowling, among others, when he lashed out at Khan immediately after a London terror attack previous year which killed seven people and left 48 injured.
Trump will be given a presentation from the MI-6 intelligence agency and military leaders to show how Britain is fighting terrorists - in an effort to convince him that May is a tough leader. "What does this man have to do to have the invitation that the prime minister has extended revoked?" He will also meet the Queen in Windsor.
Later on Friday, Trump and his entourage depart for Scotland and golf. Mr Johnson said: "He knows that he has an opportunity to make this special relationship even stronger".