We were at WDW in February. My son didn't anything at a buffet (ate a few snacks from the backpack) and they didn't charge us. A few meals (non-buffet), he shared with either me or my dh. One buffet he slept right thru. He doesn't even remember the restaurant. We just asked him if he was hunger and the waitress was willing to work with us. Something to consider. My ds had just turned 5 when we went, but he varies on what he eats. If had a big breakfast, and then lunch, he didn't always want the dinner.
Hope this helps.