As many of you have already indicated, this is a horrific act that will impact this community and nation for years to come. Having no kids of my own, I put considerable thought into whether I should modify the show as an outward acknowledgement of the event. I think we as decorators are already pulled in the direction of sort of putting our emotions in our front yards.
My initial thought was to change to Silent Night (part of the tranquil / peaceful late night rotation) with a simple voice over. Then I tried as best I could, imagine myself as a parent. After lots of debate, I came to the conclusion that my show represents all that is good and wonderful about this time of the year. My show focuses on the Good News, the joy of friends and family, and the excitement of a new year. Ultimately, I decided that it's not my place to start a discussion / acknowledgement within the vehicles of the visitors. I'm sure there are many parents who may not be ready to talk about the event, etc.
Ultimately your drawn to feelings of empathy / sympathy / prayer for the affected families with a lingering question, "is my prayer and empathy enough?"