This falls under (FAR) 14 CFR 91.15. Historically, dropping candy has been officially viewed as not presenting a hazard.
If you tape a small bit of crepe paper to each piece of candy, they will be more visible and fall more slowly.
For safety you might consider having two people in the aircraft, one to fly and one to call course changes and drop candy. Don't fly too low, too slow, and think about wind drift during the decent of the candy.
I have seen this done over a high school sports stadium.
Be safe,
Wes