Also be careful the chickens don't realize you are a food dispenser, both you and the owners will have a terrible problem keeping them in their own yard afterwards.
Honestly, I wouldn't do it. Sounds like it will cause more problems than it solves.
It always irritated me when my neighbors would throw random stuff to my chickens without asking me first-- oftentimes it was bread, which really isn't that good for them.
The chickens will be fine for a few days, even if they do not have food. Sounds like they are foraging their own food.