Hi Stephanie!
Welcome to the Disney Parks Moms Panel! I have a three-year-old who is in that stage of not-eating where one chicken nugget seems to hold him over for multiple days at a time, so I completely understand your desire to not waste precious
Disney Dining Plan entitlements on un-eaten meals.
The answer to this question comes down to the type of Table-Service meal your family is planning to enjoy. Non-buffet and non-family style dining locations, where each guest orders an individual entree from a menu of many options, are locations where you only pay for what you order. Some of my favorite 'Menu Table-Service' locations are 50's Prime Time Cafe, Sci-Fi Dine-In Theatre Restaurant, Via Napoli Ristorante e Pizzeria, and Whispering Canyon Cafe. You can go ahead and reserve any of these locations without a second thought.
Character Dining, Dinner Shows, Buffets, Family-Style Meals, and Dessert Parties usually do charge by the head as these locations are more than just refueling and resting. Accommodations of all kinds can made for those with special dining needs, but exceptions do require advanced notification of the special need. Your best bet would be to call Disney's Dining Reservation Line when booking any of these. Their number is (407) 939-1947.
Definitely stop by
Disney's Baby Care Centers where you can find a microwave and an oven to prepare any part of your son's meals. And check out Disney's info page for
Autism & Cognitive Disability Services.
We'll See You Real Soon, Stephanie!
~Kristen