I think everyone remembers the exact moment that someone told them Santa wasn't real. It was Christmas morning, when I was 7. I'd been dead certain that I had heard Santa going back up the fireplace and went downstairs to check. Saw the presents and no one around. I was so happy that I finally(almost) caught him! My parents shot that theory down as soon as I said it. Sad day.
Anyways, I don't think I would do the same to my own children. I wouldn't cold-hearted or anything. I would just tell them the story of Santa as adults know it. Tell them that they're still getting presents on Christmas morning and teach all the other traditions. The only reason they have to 'believe' is for Polar Express and Grandma Got Run Over By A Reindeer to make sense.