Mr Trump's four adult children, Ivanka, Tiffany, Eric and Donald Jr were also present.
The Republican President is in the UK for a three-day visit which includes the 75th anniversary of the World War II D-Day landings.
On Monday morning, the Trumps touched down in London and were greeted by Her Majesty the Queen, Charles and Camilla in the garden of Buckingham Palace.
Mr Trump and the First Lady enjoyed lunch at the Palace before stopping by the Picture Gallery and Westminster Abbey where the President laid a wreath at the grave of the Unknown Warrior, Hello! Magazine reports.
Just hours into the visit, Trump was slammed for failing to bow to the Queen, instead opting for a handshake.
"Did...did that man just fist-bump our Sovereign? Get him on the block," one person wrote on Twitter.
While some royal fans were horrified by such an act, there is "no obligatory codes of behaviour when meeting the Queen or a member of the royal family, but many people wish to observe the traditional forms."