We will be in Paris for a week in early Dec. Would like to take a day trip or two that would maximize experiencing the Christmas/winter season. Any suggestions?
Vaux-le-Vicomte decorates for Christmas and it's really quite lovely. I would vote against Disneyland Paris as a day trip, as we were quite disappointed at their lackluster Christmas effort. If you've been thinking of seeing the Cheateau de Fontainebleau, it would be a good time to come. The chateau itself isn't decorated for Christmas, but there are lights up all over the city, and they even pipe in Christmas carols in the afternoon/early evening on the main streets and pedestrian streets.
The Amiens cathedral might have colored light projected onto the outside after dark which shows what the cathedral looked like when all the statutes were painted. You'd need to verify if it's being done this Christmas.