12/31/2012 at 03:00 PM EST
Happy belated birthday Jude!
– who turned 40 on Dec. 29 – stopped into Sprinkles Beverly Hills on Sunday with his kids.
Wearing a beanie, hood and sunglasses, Law chilled out by the condiment display while his kids ordered treats of their choice.
"Jude was really sweet to his kids and explained to them how the cupcakes [are made]," an onlooker tells PEOPLE of the Anna Karenina
The family left the gourmet bakery with red velvet, vanilla, lemon and whole milk cupcakes.
– Jennifer Garcia