Melania Trump won't campaign "due to her schedule as a mother and First Lady," her spokeswoman said.
"I do miss Nancy Reagan. Ronald even more. Speaking of 'Bedtime for Bonzo,' I think even that chimp stood up straighter than Michelle."
The president and first lady will have tea with the Queen.
Criticism of the Trump administration policy separating families at the border is growing, and across the political spectrum.
The former first lady said she was concerned for women after Hillary Clinton lost in 2016.
Former first lady Michelle Obama has been on the cover of Vogue three times.
The retired general tweeted about the now-vacant President's Council on Fitness, Sport and Nutrition, and that Ivanka Trump should "check it out."
"The best qualified candidate in this last race was a woman," Michelle Obama said.
Will they be paid as much as Ryan Murphy and Shonda Rhimes?
The book will detail her childhood as well as her time in the White House.
"Young people will finally see superheroes that look like them on the big screen," the former first lady tweeted.
"We miss you guys, and we miss the way those who worked with us on this incredible journey carried yourselves," the former president said.
"I tried to negotiate less gray hair, and Kehinde's artistic integrity would not allow (him) to do what I asked," Barack Obama said of the portrait.
Melania Trump was the only Trump family member with a higher favorable than unfavorable rating.
Michelle Obama turned 54 on Wednesday.