Oh Darleen, I too remember trying to travel with little ones and bringing all the diapers and formula and food! But things have changed and when I started traveling with the grandchildren I realized how easy it is in the modern world of convenience!
You have several options to make your life easier for your vacation. You can simply ship a box or two of things you will need during your vacation such as baby diapers, wipes, food, etc directly to your resort. I suggest you ship for the arrival to be no more then 3 or 4 days before you arrive. Address the boxes with the name the reservation is under and include the arrival date. You can find the resort addresses on their main page at the Disney website, for example click H
ERE. You will see the address on the right side of the page.
Your second choice is to use one of the grocery delivery services available in the area. I have used and love gardengrocer.com many times in the past. They have an extensive list of baby needs to select with many different brands. You simply register with them, select the items, charge using a credit card, select a delivery date and resort location, and it will be there when you arrive or shortly after. It couldn't be easier!
Most of the resorts will have a small store as well where you can find a small sampling of baby needs. You won't have much of a choice for brands so please be aware of this. Also, the baby centers in each park have food and formula and diapers for sale in case you forget these important items on your way out to the parks in the morning!