You should tell your children about Santa. Rather or not they will believe it or not, You should. Assuming this is for some parent, This would be a good idea to get them to behave like the classic: "Behave well and Santa MIGHT give you that xbox" etc. Besides, It'll let them have hope until they grow over and realize the truth.
Like you, And many other older people now, Let them have those childhood beliefs.
Me and my brothers were never told about Santa, Easter bunny, Tooth fairy, Etc. My family told us the truth right on.
I'm in high school but either way they are going to be happy getting the gift if they knew it was from you or from Santa. So doesn't really make a difference to me- I would just be truthful.