Actually there are a lot of healthy choices the the CS.
Just be careful with the sauces and condiments. Only once did I have problems with barbecue sauce with Mom. I now have learned how much she can have and give her less. Salad dreessings tend to have a lot of soy, salt, sugar and/or fat. sigh.
Here are some counter service examples.
Toy Story Pizza
Pizza Planet Chicken Salad - Mixed greens, grilled chicken, cantaloupe, cucumber, red onion, tomato, green peas, fresh basil and balsamic vinaigrette $7.19
Caprese Salad - Mixed Greens, red and yellow grape tomatoes, mozzarella, kalamata olives, cucumber, fresh basil and balsamic vinaigrette $6.49
Electric Umbrella
Tossed Island Chicken Salad with mango, pineapple, and raisins, in a fat-free Italian dressing $7.19
Vegetable Wrap with hummus, zucchini, lettuce, cucumber, carrotts, roasted red peppers, balsamic vinaigrette and apple slices $6.79
Toluca Lakes Turkey Company
Turkey Leg $5.49
Nine Dragons
Sha Cha Beef Skewers - Savory beef flavored with Sha Cha sauce $7.99
Easy on the sauce
Canton Pepper Beef -- Sliced beef stir-fried with onion, green and red peppers. $13.99
Sunshine Seasons in Epcot has rotisserie meats, stir fry and salads
I have celiac so I use lettuce or corn tortillas to wrap a hot dog or burger. You can reduce carbs by asking to substitute (sometimes that does not work), asking them easy or no sauce, and hold the bun. There are many articles and guides on the internet for people going to WDW. There are many counter service options out there.