Power
Yeah, you're not actually Santa (hopefully this isn't coming as a surprise), but it's still your job to play a convincing one. You're playing a cultural icon, one who can even influence the behavior of young kids. If anything, don't you think all of those exhausted parents deserve your help?
After all, besides mom, dad, and Superman, Santa Claus may be the biggest role model for American children. Just look at the story: he's a jolly old man, he helps children realize their dreams, he travels all over the world, and he's always watching you.
This is a powerful position, and someone has hired you to fill it in their local shopping complex, downtown festival, or holiday parade. That means (at least to children) you have all the power of one of the greatest authority figures in their lives. Sure, you're going to use that power for good and you'll totally deal with the millions of pictures and bratty children and spoiled parents, but if anyone truly steps out of line, all it takes is one word from you:
Coal.
The most powerful word in any Santa's vocabulary. Use it wisely.