There's a bunch of Christmas'y type activities and displays around downtown that run during December like the Christmas market at QE theatre, carol ships, Christmas train/Bright Nights in Stanley Park, Christmas tree displays at downtown hotels, Santa Claus parade, public skating at Robson Square, and displays at Canada Place. Just outside of outside of downtown but accessible by bus are stuff like Van Dusen Garden's Festival of Lights and Grouse Mountain's Christmas at the Peak.
The winter is likely to be pretty mild due to El Nino so it's likely to be more wet than icy/snowy.