That is a good question? Why? Because, speaking as a sociologist and social psychologist, I can tell you that whatever the majority does appearing as 'normal' it is difficult to be against it. Jesus knew this and though He was as both a man and God, the situation was not easy to deal with or face on His own but he had to do for our sake.
I remind you of this because whenever we/you have to face a majority of people who are doing or practicing something and we/you know that is not godly, we/you face being bullied, and or being persecuted. People don't like their sin being called out. At the same time, we feel we should belong to a group, and we should. We as Christians are members of the body of Christ. However, we see among us the worship of false gods. People with good intentions do this, we have 'American' traditions of this.
Belonging to a group is an important aspect of identity. Again, we want to belong, we want to do what everyone else does because not belonging and feeling on the outside of society is very difficult for an adult and certainly for a child. That is why, we as Christian parents, have to be strong in our faith and demonstrate this to our children.
With so much commercialism around us and a part of our American life style, it is difficult to not be part of it. Santa Claus was a created figure by certain elites to draw people together into what we know as a civil union or civil religion. There is nothing Biblical about Santa Claus. Our children should know this. Does that me we should forbid our children from singing songs about Santa, or from sitting on his lap to get a picture with the family, or from hanging a stocking by the fireplace with hopes that St. Nicholas will be there?
No, but when we do it 'religiously' and without Christ in our Christmas then it is not a good practice; especially, if we want our children to grow up to be good Christians, to be saved! It is wise to children and grandchildren that Santa Claus is a man made symbol used to promote giving which is a good thing (the Magi brought gifts to Baby Jesus) but without hope of eternal life through Jesus Christ, it is an unwise symbol that could be idol worship. I also tell them that many people in the world are not Christians and we should pray for them so that they reach out to the Lord Jesus Christ. And, I stress that when we look upon that man made symbol, we should first should think of Jesus Christ who is the greatest symbol of love, giving and hope.
There is no point to demonize 'Santa Claus'. Why not demonize him? If children have a sound faith in God they will see for themselves who the false gods are. And, they will not be drawn away from the true God because they feel outside of the 'normal operations of society'. Best to prepare your children for living in this world with the Word of God, so that they can redirect social norms toward the truth - one body in Christ the Lord.
Mostly, you want your children to know unconditionally that Jesus Christ is their Lord and Savior and that all things are possible in Him! Glorify the Lord! Sing songs of praise to Him. Place a manger scene under your tree and talk about the love and peace we have in Jesus Christ!