I raised 2 children here in California, and we've been active in a Conservative shul. The majority of my kid's friends didn't go to church, or Sunday school, and so all they did on December 25th was exchange gifts and eat. By the time they were teenagers these kids had learned a bit about why they were doing it, but it was all pretty secular. Because we always answered my kid's "why" questions pretty thoroughly, sometimes they had a better idea of why people celebrate Christmas and Easter than their "Christian" friends did. We've always taught our children that sharing a meal with their friends and helping them celebrate their holiday was OK.