You can get whole apples at kiosks everywhere, as well as sliced apples from at least one or two kiosk type locations in each park. The sliced apples usually come with other cut up fruit. Disney has really stepped up the availability of healthy snacks, which makes me very happy! We eat fruit every day while in the parks, and I have zero desire to carry any around with me. I prefer to buy them as we go. I never carry a bag into the parks or anything, so it would be pretty hard to carry four apples in my pockets, lol!
Apples are pretty packable for traveling though, maybe throw a few in a suitcase so he can at least have one handy in the room for the mornings. I always grab one as we head out for the day (club lounges have them) and I eat it as we walk, monorail, boat or whatever to the park.