Michael Phelps' Mom Says Baby Boomer Is Set for His Rio Debut

"I told him how proud I was of him and what an honor it was to be selected by his teammates," Debbie Phelps tells PEOPLE

Photo: Mark J. Terrill/AP

Michael Phelps‘ mom, Debbie, was dozing off Tuesday night, resting up for the long flight to Rio, when a text came in from the greatest swimmer of all time, telling her to wake up early for a “big announcement.”

Then, giddy, he couldn’t hold back any longer. “I was elected to be the standard bearer,” he typed.

“He was so excited,” Debbie Phelps tells PEOPLE. “I told him how proud I was of him and what an honor it was to be selected by his teammates.”

Phelps, 31, was chosen late Tuesday by a vote cast by the U.S. Olympic athletes. He will carry the nation’s flag in the Opening Ceremony Friday, wearing a custom-illuminated USA blazer.

His mother and fiancee, Nicole Johnson, three-month-old son Boomer, and soon-to-be mother-in-law, Annette Johnson, were scurrying Wednesday to get tickets for Friday’s big event, which they hadn’t expected to attend.

“I can’t stop crying,” Annette Johnson tells PEOPLE. “We’re so proud of him and so excited to be there.”

Johnson says that while Phelps is getting focused for his swim events, his family is busy arranging a shipment of organic diapers, packing a car seat, baby clothes and a carrier emblazoned with the American flag and Phelps’ name.

“Boomer has a bigger suitcase than all of ours!” she says.

Does Michael Phelps Already Have a Future Olympic Swimmer on His Hands?!

Debbie Phelps tells PEOPLE that the fifth and final Olympics for her 31-year-old son has her feeling “reflective.”

“I’ve been thinking over his whole career from a fifteen-year-old to a mature man, how he’s written the history books for his sport,” she says of her son, who heads into the Rio Games as the most decorated Olympian ever, with 18 gold medals, two silver and two bronze. “It’s been emotional to think back on all those moments. Every time I go someplace, someone has a story about how Michael is a part of their lives.

“I was just thinking about Katie [Ledecky] meeting him in Virginia when she was 10 and asking for his autograph, and now they’re teammates returning for the second Olympics together. It’s really been incredible,” she added.

Phelps has made a remarkable turnaround in his personal life since entering rehab after a second DUI arrest in 2014. He was also voted co-captain of the swim team for the first time.

Now, the star swimmer has a chance to add to his historic Olympic tally starting Aug. 8, when he swims in three individual events: the 100-meter and 200-meter butterfly and the 200-meter individual medley. He may be chosen for up to three relay races as well.