The family documented their time at the amusement park in videos posted to Instagram Stories.
"We are on a family trip in Paris and I would love to know if you could guess where we’re going," Williams said in one video, which was taken in the car heading to the surprise destination.
Once the family arrived they were still mum about revealing their location in a video taken at the opening gates of the park.
"So we’ve arrived on our destination," Williams said. "She [Olympia] doesn’t know where we are."
After revealing their magical location, fans got a sneak peek at the family's fun-filled day. From rides to hanging out with The Evil Queen to donning some sparkly sequin Minnie Mouse ears, it's clear the group had a wonderful time.
"Who’s that pretty baby with the Mickey Mouse ears?" Williams asked of her adorable 9-month-old daughter at a restaurant in the park in another video.
Ohanian, 35, also posted a photo. "Caught up with T'Challa," he wrote alongside a snap of himself with the Black Panther character.
This family adventure comes less than a week after Williams announced her exit from the French Open due to a chest muscle injury.
"It's extremely disappointing," Williams told reporters at a press conference Monday. "But also, I made a promise to myself and to my coach and to my team that if I'm not at least 60 percent or 50 percent, then I probably shouldn't play. The fact that I physically can't serve at all is a good indication that maybe I should just go back to the drawing board and stay positive. And try to get better and not get it to a point where it could be a lot worse."
Williams took to Instagram to thank her fans following the announcement.
"You always live to fight for another chance. I’ve done a lot of fighting and this is just the beginning. Thank you a for the support. I love you," she wrote.
The French Open was Williams' first major tournament since giving birth last year. According to her coach, though, Williams is expected to compete in Wimbledon this July.
"It’s a muscular injury, and if she had continued here, it would probably have become a tear,” Patrick Mouratoglou told The New York Times. "So in 15 days, it should normally be healed, and she will be able to play again."
Williams recently spoke to ET about the "mom guilt" that comes with returning to tennis. Here's more on that story: