For most children Father Christmas is just a fantasy figure which they grow out of believing in. The reason the church has gone to so much trouble to include Father Christmas is less innocent. It is not accidental that Santa clause is presented as a Father.
Young minds come to believe that all good things come form this Father at Christmas if they are good. Of course they grow out of it. But their minds have been primed to believe in a mystical father figure. A Father who they have strong emotional reason to believe in because they associate the belief with pleasure. It is one small step to then replace this Father figure with another Father who will reward them.
The Father at the church will be pleased to confirm the existence of an invisible male deity whom they can call the Father. For those that believe it is good for young minds to be primed to believe in a male Father deity this is seen as a good thing. For those who believe that such beliefs will separate them from their true identity in later life, it is not such a bright idea.
Children should have fun and many will think that only spoil sports would examine the psychology of this myth so deeply. That is what the church wants you to think!