Dressing up as Santa's little helper is a fun way to fool the kids. But you have to have the costume exactly right so as not to arouse any suspicions. Don't forget your elf shoes, which you can whip up out of leftover costume fabric in a few minutes.
get some blue under pad (for sleeping bags) to wrap a shoe or old sneaker (try to use a pair with black bottoms/soles). Note: make sure you use a pair of shoes that can be put on and off quickly (like slippers). You may also need to leave a flap in the top front with velcro to allow opening and closing around your ankles (helps to keep them on your feet. Make sure you leave room at the bottom of the foam to allow for the sole of the shoe to contact the ground.