Hey, by the way, y'all, I'm not going to ask or instruct my children to lie to your children because you choose to lie to them. I am also not going to lie to them.
Now, don't get me wrong. No one in my household is going to go out of our way to tell them that Santa Claus isn't real (and that you lied to them), but if it comes up, the younger members of my household are probably not going to be able to gracefully deflect the conversation, thereby casting light on your lie.
Deal with it. Oh, and stop lying to your children.