Mariah and Nick's roller-coaster of love

Singer gets 'the best surprise ever' from husband

Nick Cannon knows how to show his devotion – Mariah Carey's 17-carat engagement ring is proof of that.

But his love was on full display again Tuesday night, when Cannon rented out Six Flags Magic Mountain in Valencia, Ca., and threw a surprise bash for his new bride and 100 of their friends. (Price tag for the five-hour rental runs in the six figures.)

"This is wonderful," Carey told the staff as she entered the theme park. "The best surprise ever!"

Their first order of business? Taking a spin on the Tatsu, one of the park's famous roller coasters. After posing for photographs, Carey downed her class of Chardonnay before they both jumped on the ride.

Five inversions, 62 miles per hour, and 3.5 minutes later, the happy couple and about 12 friends returned to solid ground. "When they got off the ride, Mariah wanted gum so Nick unwrapped a piece and fed it to her," said a guest. "He is head over heels."

Carey's staff quickly fixed her wind-blown tresses and smudged makeup, then the camera-ready pop star – wearing Louis Vuitton jeans and peep-toe pumps – hit up the carnival games with her hubby. (The clearly besotted Cannon stood by her side the entire time they shot hoops.)

"They were so affectionate," said a guest. "It was like watching two teenagers in love."

The private party had countless Carey touches, including candlelit tables, lavender and pink balloons (her favorite colors), and faux butterflies placed in the vases and hand painted on cupcakes. The wood sign in front of the Grand Carousel read "Nick and Mariah – A Love Story."

Guests, including Cannon's mother, brother and manager Michael Golman, dined on theme park favorites like hamburgers and pizza while an open bar kept the Hess Cabernet Sauvignon and Chardonnay flowing.

By Kimberly Lansing