I haven't had surgery, but DH & I go regularly with our neighbor who had gastric bypass in Nov 08, just before Thanksgiving. It was laproscopic surgery.
When she first got back into park trips she always made sure to pack a small bag with things she could eat and carried a protein drink with her. Actually she still does that. She needs to eat more frequently than we do so she brings small prepackaged portions of foods that work well for her.
For meals, at first we stuck to fast food places that offered options like the 1/2 chicken meal you can get at Sunshine Seasons at Epcot or Cosmic Ray's. Either DH or I would order the chicken meal and our friend would eat a small piece of chicken and a few of the veggies. That still left whichever of us who ordered the chicken meal with plenty of food. Some of the fast food places also have bowls or cups of soup available, depending on the variety of soup that was good for her. In sit down restaurants she usually orders an appetizer as her entree and takes home a doggie bag. She carries the card she got from her surgeon and the WDW chefs, and chefs at any off property rest. we go to have always been very helpful to us, and living in the WDW area, we get there as often as we can.