I believed in Santa too my friend. As long as you teach the children the 'TRUE' meaning of Christmas and the 'Reason for the Season' I see nothing wrong with adding the story of St. Nick aka Santa in there as well. There really was a St. Nick also. Once children get older, they tend to find out from their friends or older siblings anyway. Look at us; we didn't turn out to be a mass murderer because of it did we? I see no harm in it. God bless.