Aguilera was photographed with the smiling 2-year-old in Los Angeles on Thursday, the same day news of her divorce filing broke, and a close friend of the couple says she intends to keep up a brave face.
"She's focusing on continuing to be a great mom," a close friend of the couple tells PEOPLE. "She's spending as much time as she can with Max."
Adds the friend, "Max is her No. 1 concern. She's making a huge effort to continuing to be a good mom through this transition for him."
A major challenge for the couple will be co-parenting during the divorce process, but the pair plans to work together.
"It’s hard," the friend says. "You've got to handle it with dignity. I don't think they've figured out everything yet. They have a child together, so they're trying to do what's best."
A Fun OutingKeeping Max happy means going out for fun outings even when the world's attention is on her. That's why the two spent time at Mr. Bones Pumpkin Patch in West Hollywood on Thursday.
Dressed casually in sweatpants, a hat and big sunglasses, Aguilera, 29, threw herself into the pre-Halloween fun.
"Christina was in a cheerful mood and seemed to have a blast with her son Max," says an onlooker. "It was obvious that Christina was trying to have a fun outing and make things special for Max. Max looked very happy to be out with his mom."
During the visit, the pair spent time on the super slide and were "screaming with laughter," the onlooker says.
As for the singer's demeanor, the onlooker says, "Christina looked anything but sad and it's hard to believe that she is going through a difficult breakup. She seemed very strong and just focused on keeping things normal for her adorable son."
Regardless of how tough it gets, though, Aguilera plans to keep up the hands-on approach to motherhood, the friend says. "She wants to be the first face Max sees in the morning, and the one to put him to bed at night."
Reporting by PERNILLA CEDENHEIM