As the We're the Millers star, 43, caressed her fiance's face, she gave onlookers a glimpse at her giantengagement ring from her love of more than a year and a half.
This summer, a source close to the pair told Us Weekly Aniston is set on a "destination wedding" for her big day, "kind of like eloping with a few friends."
"There will be the feeling of a vacation, since that's their favorite thing to do [together]," the source revealed.
"Jen is over the moon about her second chance at a happy marriage," another source says of the Horrible Bosses actress, who divorced Brad Pitt in 2005. "Justin is giving her a solid vow to love."
Theroux proposed to Aniston on Aug. 10 in NYC while he was celebrating his 41st birthday.
Theroux's rep told Us, "Justin Theroux had an amazing birthday Friday, receiving an extraordinary gift when his girlfriend, Jennifer Aniston, accepted his proposal of marriage."