DD was 11 last year (but tall for her age and looks older) and she just decided that it was more fun for her to give out the candy to the little kids. She really enjoyed seeing all the costumes and trying to get them to ask "trick or treat".
Now DS, on the other hand was 13 and he and his friend went out for a little while, but I thought they were too old to be running through the neighborhood in camo costumes...and everyone was still leary of Sept 11 at that point. It made me very nervous.
what I can't stand is after all the little ones have stopped and you have pretty much turned off the lights, etc, , because it's getting too late, and the older kids come and ring the doorbell anyways. They look like such hoodlums sometimes.