making Christmas tree decoration (you could make this several activities by specifying an angel, a bauble, a reindeer, etc)
Looking through their toys to find old, but nice ones, to take to the salvation army
Taking said toys to the salvation army (or local hospice, etc)
making truffles as gifts for the neighbours
learning a Christmas song
writing letters to Santa
making a gift (drawing or handprints) for Daddy
making a gift for Granny, etc etc