"Canada🍁 photo dump 🇨🇦," McPhee captioned a series of photos from Foster's home country, where she was also accompanied by her mother, Patricia.
One image shows McPhee adorably waving at the camera as she holds Rennie in one hand as they take a walk surrounded by flowers. In another, the doting mom gives Rennie a kiss on the cheek as they stand waterfront.
While McPhee has teased photos of the baby in multiple posts since giving birth in February, this is the first time she showed her son's face.
Foster didn't let the opportunity to gush over his wife pass him by. "HOT MOM!!!!" the 71-year-old record producer commented, adding the flame emoji.
McPhee also got in on the fun, bragging about her husband in multiple Instagram Stories. "David made a visit to his childhood piano," she wrote alongside a video of Foster playing the instrument. "Was so cute."
In a second Story, she wrote: "Still got it. My cool guy."
Ahead of the arrival of Rennie, McPhee spoke with ET and dished on how she was feeling amid her pregnancy. "I feel really good," she said. "I'm in a good place."
McPhee also opened up about how being on set with children for her Netflix series, Country Comfort, helped get her ready -- and more excited -- for motherhood. "Being on set with these kids every day on the show... seeing the different stages of their life is just something to look forward to," she explained. "There's always going to be a different stage to look forward to as a new mom."
For more on McPhee and Foster, watch the video below.