I don't see either side of it at all. Of course you want to be truthful to your kids but they will figure out that Santa isn't real in their own time (or if you want to tell them when they're not kids anymore) and I guarantee they'll be thankful you played along. When I believed in Santa it was the best feeling ever on Christmas day when he came around. Little me would have been devastated if my parents told me, as well as making the whole event of Christmas much less magical and much more dull.