MIL asked us this question before we even had a son. "You aren't going to make me lie to my grandkids about Santa, are you?" She never "did" Santa with DH. Yes, b1tch. And if you don't want to, then you don't have to be around for the holidays. My step-mom told her boys the truth about Santa, but she has always been supportive of our family traditions. MIL, not so much.
Anyone else have close family that doesn't want to lie to your kid?