Looks like Kourtney and Scott put their differences aside for the sake of the kids, on Sunday, as the family headed to lunch together at The Grill in Calabasas.

Their faces were somber, to say the least -- even Mason was out of sorts, while Penelope looked a bit distant from her day (so sad!).

Kourtney tried to keep her chin up, according to our photographer: "Kourtney was trying to keep everyone motivated and get the kids to interact with Scott. Scott basically looked like he'd rather be doing something else. The whole situation was awkward."

Maybe it's not such a happy new year for the Disick-Kardashian clan ... Wonder what 2016 will bring!