Hi Stephanie! Many guests enjoy having extra snacks and drinks in their resort rooms during vacation. It cuts down on the money spent and time used to hunt down food that the family might not even enjoy. Having what you like is a perk that we all wish for.
The outside grocery delivery service that I have used and like is called gardengrocers.com. You can find them on line and they have an extensive list of food items as well as other supplies vacationers might need. You must meet a minimum but that is not usually hard. You will pick a delivery date and then your work is done. They will deliver to the resort and if you are not there the Bell Staff will take and store your groceries including anything perishable.
Please remember that the Disney resort rooms will all have small refrigerators but they are certainly not adequate to store much or anything that needs a high cooling temperature. If you are lucky enough to book a DVC room or a
Fort Wilderness Cabin then you will have a full size appliance.
Every resort will also have basic supplies in their shop such as bread, breakfast items, milk, juice, and lots of snacks in case that it easier.