During the romantic getaway, the couple also celebrated at Sugar Factory American Brasserie and Chateau Nightclub & Gardens at Paris Las Vegas.
Britney and Jason, her former agent, have been an item since 2009, and he reportedly popped the question with a Neil Lane ring Thursday, his 40th birthday, during a romantic private dinner.
"She's really happy," a source tells ET. "It's going to be a great weekend."
According to People, celebrity jeweler Neil Lane designed the engagement ring with a princess theme in mind. A round white diamond sits in a handmade platinum setting with 90 small diamonds around the eternity band.