Dressed in a snug black turtleneck sweater with black leather pants and knee-high black boots, Simpson, who was described as "very courteous" by bystanders and arrived in a chauffeured SUV, looked stunning as she enjoyed a meal with her family.
"She is one kind and warm individual with an electric smile that lit up the dining room," a bystander who chatted with Simpson, 41, told PEOPLE.
The family — who was joined by an assistant — ordered two pizzas, as well as soft drinks and a beer. The kids played with pizza dough while they waited for their meals. "The kids were very well behaved," the source told PEOPLE. "Everyone was just amazing."
Before leaving, Simpson took individual photos with every staff member, and even autographed a t-shirt for the restaurant. Johnson, 42 — who wore a Boston Red Sox hat — "left a very generous gratuity to the server," PEOPLE was told.
The other parties in the restaurant were starstruck by Simpson, who "smiled at everybody."
"Nobody asked her for an autograph, but I'm quite sure she would have accommodated anyone that did," the source said.
One of my classmates ran into Jessica Simpson & her husband in Boston! 💋 pic.twitter.com/rx6cC8U6y6
— •~🌻~•Kelley•~🍁~• (@KelleysCreation) September 25, 2021
Simpson was also spotted in the Faneuil Hall area, where she took photos with fans in front of Quincy Market. Sporting sunglasses on her head and large, diamond-encrusted hoop earrings, Simpson was all smiles.
Johnson was raised in nearby Needham, Massachusetts, located about 20 miles outside the city. However, Simpson mentioned to fans that the family was in town for the Laver Cup, the popular tennis tournament held all weekend at the TD Garden. The event featured legends of the sport like John McEnroe and Roger Federer, while stars like Mariska Hargitay and husband Peter Hermann watched.
When they're not busy with the kids, Simpson and Johnson have plenty of fun on their own. Last month, the couple celebrated date night with a sexy snap as they prepared to head out for an evening together. Dressed in a fitted leopard dress and heels. Simpson posted for the camera alongside Johnson, who wore a dark-colored suit with a blue shirt underneath.
"Happy wife. Happy life. Ladies and Gents it's date night 💚🙌🏼," Simpson captioned the post.