http://www.target.com/IGLOO-Maxcold...se=0&index=target&rh=k:igloo back pack&page=1
This is not the exact cooler we bought but it’s similar.
This is what we do on lots of trips. It has saved us a lot of money (and fat and calories) over the last few years.
We spent roughly $25 at Target and bought an Igloo brand insulated, back pack cooler. It’s very lightweight and insulated to keep things cold.
While at Target, I took the backpack to the aisle where they have the Rubbermaid containers. (Like Tupperware) I bought a large rectangular container that would fit inside the insulated back pack. I chose the biggest one I could get that would fit. Be sure to leave room for a blue ice. You can try all of these things out for size before you leave Target.
I make sandwiches at the hotel and place them in the Rubbermaid container. When we’re going to the parks, place the blue ice pack and the Rubbermaid container in the insulated backpack. It stays cold until lunch time and all is well. It keeps the sandwiches from being smashed. I also put a can of Pringles in the outer holder where you should place a bottle of water. So, Pringles and sandwiches for lunch.
When the Pringles can is empty, you can keep it for the next day to use as a container if you want to refill it with cheetos or something else you don’t want to get crushed.
This works well for us not only for Disney but also trips to the zoo etc.
For drinks, those in our family who drink soda buy a soda for lunch and also Disney will give you a glass of ice water free at any of the counter food services if you don’t drink soda. Crystal light and many others make those single serving powder drink mixes if you don't like the taste of water.
I also stash a few wet wipes into the pocket on the outside of the cooler backpack. I've also taken little cups of applesauce in that cooler pack as well when we took little nieces and nephews.
I hope this helps. It has saved a TON of money over the last few years for us. Have a great trip!