"They walk around holding each other's hands and are always very affectionate. [They're] always smooching," the eyewitness said, adding that the couple, who are "clearly boyfriend and girlfriend" get along great and "like to cuddle."
Carey and Tanaka were spotted shopping together at Moncler, a high-end store in Aspen, on Monday, and will remain in the area until just before her Dec. 31 performance on ABC's Dick Clark's New Year's Rockin' Evewith Ryan Seacrest in New York City.
"They're having an incredible and romantic trip and enjoying some relaxing family time before she heads off to perform in Times Square for New Year's Eve," a source tells ET.
Carey is clearly comfortable with Tanaka spending time with her children, 5-year-old twins Moroccan and Monroe.
According to another source, Tanaka is "great" with the kids and they like him a lot. "They all dance around together," the source says, adding that Carey and Tanaka "are affectionate in front of the kids as well."
"As he normally does for the holidays, Nick Cannon will be joining Carey, Tanaka and the kids in Aspen later this week," the source reveals.
There will be plenty of room for Cannon when he arrives, as Carey and her crew are staying in a sprawling five bedroom, five bathroom home, courtesy of Airbnb.
The singer's home for the holidays includes a wood burning fireplace and two living rooms, as well as a game room complete with a wet bar and pool table. The home also includes a gym, sauna, and wine room, and a hot tub with views of the surrounding snowy mountains.
Though Carey just arrived in Aspen, her holiday celebration with her kids kicked off over the weekend. The "All I Want For Christmas Is You" singer got a special visit from Cannon and their twins while performing at New York City's Beacon Theater on Saturday.