I just thought of something else.
Not knowing what PetSmart is expecting this may not be something they want but here goes.
What if on the days you are there with the adoptable pets you also had a big box, with a list of things that are needed in your shelter, that are sold in PetSmart. You can attach the list to the box (in big writing), and have a few extras for people to take in the store. Or they can take a picture of the list with their phone. This could also help your organization if you are getting low on certain items, you could stress this on your list.
While they are shopping they can pick up an item(s) to go in your organizations donation box.
I don't know if PetSmart would see this as big enough benefit to swap off with the food, but maybe? It would help your organization, right?
#PetHealthandNutrition