The invitees to Sandra Bullock’s Fourth of July barbecue at her Austin, Texas, home were strictly A-list, including Jennifer Aniston and her fiancé, Justin Theroux, and Sandra’s longtime pal Jason Bateman.

But the guest of honor, as always, was her son, Louis, 5. “Her main occupation is as mom to Louis, who is about to enter kindergarten,” says an insider. “She’s never been happier or more at peace with her life.”

sandra bullock with son

Sandra with her son Louis in Italy in 2013.

Sandra’s certainly come a long way since her painful 2011 divorce from adulterous motorcycle enthusiast Jesse James, 46. “Their marriage was such a train wreck,” the insider says. “It changed her world view. It takes a lot to win her trust and support.”

RELATED: Sandra Bullock Confesses She's "In Love"…With Her 5-Year-Old Son, Louis!

But Louis, whom she adopted in 2010, won her heart and is now the only man in her life. “Sandra hasn’t dated anyone seriously in years and she’s fine with that,” the insider says. “She’s so busy with Louis, it doesn’t even matter.”

sandra bullock minions

Sandra at the premier of 'Minions' in June.

Motherhood has also changed her perspective on work. “She’s cut way back on the amount of film roles she does,” the insider says. “She’s now down to less than one a year.” And her one big screen gig this year, giving voice to evil genius Scarlet Overkill in Minions, was all for Louis. “He went to the premiere and laughed hysterically all the way through the film,” the insider says. “She was beyond thrilled. Louis’ excited response was all she needs.”

To read the full story on Sandra and her son, pick up the new issue of 'Closer Weekly' on newsstands now!