We flew Southwest when we went at the end of January...I'm not sure which airline you are flying. We, too, used DME, and so we didn't have a way to go off property to get food for our room. Southwest allows each passenger two fee-free bags, which worked well for us. My family of 4 each had a suitcase, and we brought a 5th suitcase for snacks/food for our room. On the way home, since we had eaten all our snacks and food, we had room in this 5th suitcase for dirty laundry and souvenirs!
We packed a lot of the same things as the previous posters. We also packed the individual little boxes of cereal and we packed shelf stable milk (I think we used the Horizon brand). We double bagged the milk in ziploc bags to make sure there were no spills, and we had milk for cereal and to go with other snacks. The shelf stable milk fit perfectly in the small refrigerator in our room.
Have a terrific trip!!