Richard, You're right Christmas trees and Menorahs are not "idolatry" because they are symbols of significant celebrations, to children too. We don't worship the symbol. They are also symbols that are unavoidable at year end. Such symbols are everywhere. Should they be taboo in a public sector setting if no one complains?
How do you shelter your child from Christmas and Chanukah? And what would be the purpose of doing so? Better that we promote tolerance than suggest either observance is taboo, to kids. Public display of such symbols would become an issue if someone voiced an objection. I would likely object if, during Ramadan, if my kids were required to stand on the school lawn and stare toward the Mecca (or mosque?). The objection would be based on the fact that I don't know what Ramadan stands for, and I don't know if I like what some of Islam stands for. The secular symbolism of the Menorah and Christmas tree have become, in many ways, Americanized too. So why avoid them?