The Nutcracker ballet matinee performance just before Christmas is kid central. Any fidgeting, screaming, crying or other nontraditional theater behavior by your offspring will disturb only the other, already harried, parents. Afterward, take them backstage to meet the dancers. All are welcome. A six-year-old we know got her ballet shoes signed, took them home, built an impromptu shrine to them and didn't stop talking about the encounter until after Valentine's Day.