The amount of candy definitely changes the capacitance! That's one of the reasons we had to add the auto-zero algorithm to the code. As the candy level decreases, the overall capacitance decreases too. Even without the candy influence, the change in capacitance is only roughly 5% from no-hand to hand-in-Jack-O-Lantern states. (This is Mike from NerdKits.)
So you could also have it ping you when the candy bowl needs refilling - sweet!
use a attach the mcu to a bluetooth module and when the candy becomes low, send an alert over bluetooth to your smart phone/computer!!! Wonder if i can buy the parts in time...