Gwen Stefani and Gavin Rossdale brought their sons, Zuma and Kingston, up to Mammoth in Northern California for a weekend of fun in the snow. The foursome threw on their cold-weather gear to hit the mountain yesterday, with Gwen and Kingston heading down the slopes on a tube. Kingston then laced up his boots and joined dad Gavin for a round of skiing. The Stefani-Rossdales got a taste of Winter after spending the last month at home in LA, where Gwen is working on her new album with No Doubt. She's also found time to record her first ad as the new spokesmodel for L'Oreal Paris, leaving Gavin to have some boys-only outings with Zuma and Kingston.