Archbishop ViganĂ²: Let us never stop honoring the august Queen of Heaven, the Immaculate Virgin - LifeSite
It is through the Omnipotence of God that the Virgin Mother is awarded the most ineffable privileges, such as to make her the One who is Blessed among women, our Co-Redemptrix and the Mediator of all Graces.
The worst part I think, other than the lying itself, is that you introduce the risk that the kids assume Jesus is a lie too.
"Well He must just be like that Santa guy!"
As an aside, I find it funny when the militantly anti-Christmas, anti-Christ atheists say that Santa is used to warm kids up to religion/Jesus Christ. Like, huh? Why not just start with Jesus? Santa definitely isn't our guy, lol. He's who the atheists worship until they get too old and move on to his anagram ;)
And I would likely do the same if any kids who already believed asked me. I'm not looking to be the asshole who ruins Santa Claus for a bunch of innocent kids just having fun, but I also refuse to lie. Got to be smart about it.