Hi Rebecca! Thanks for stopping by to see us again at the Disney Parks Moms Panel.
Planning to have some staples on hand for your family is a great way to save time on a busy Theme Park morning, and also to help manage your budget. You do have a couple of options for picking up milk for your little ones.
First, if you're staying in a Walt Disney World Resort hotel, you'll find refrigerated cases in the quick-service dining areas that carry things like milk, yogurt, juice and other perishable items. You should find half-gallon containers of milk that you can buy there and store in your in-room refrigerator. While you're there, you can also pick up your cereal, muffins, bread, fruit and other necessities.
Another option is to pre-order your supplies from a local grocery delivery service like Garden Grocer. I haven't personally used them because my family lives within driving distance and can usually pack up everything we need in our car, but I know many of my fellow panelists use them. If you search "Garden Grocer" here on the Disney Parks Moms Panel website, you'll see lots of advice from the Disney moms on how to make use of this service.
I hope this helps with your planning, Rebecca. Do come see us again if you have any more questions as you plan your practically perfect Walt Disney World vacation.
Keep Disney Dreaming,
Kathy K.