We just got back from spending a week at WDW.
Walmart delivery is excellent. Our plane landed at 12:30, we were at the resort by 2:30, and our groceries were delivered at 3:15. Walmart has 1 hour windows for delivery, and they text you when they pick up your order, and again when they are pulling into the resort. The produce they brought was all in perfect condition. If you want to take an Uber to Publix, the cost is around $10 each way.
We made all our breakfasts in the hotel, and got a few easy things for dinner on the nights we didn't want to go out. Dinner options for arrival night are pretty slim if you don't like the food at Sana'a. You can mobile order in the morning for a pick up time that evening. Or order from the airport so it is ready when you arrive. Otherwise, the wait times are at least an hour, and even longer on the weekends. We loved the butter chicken potjie. It is not too spicy. And their bread service was excellent. For your son, they had a kid's menu with pizza, a cheeseburger, chicken and rice, or butter chicken plus two sides, including a nice fruit cup. The kid's meal also comes with apple juice or milk.
The grocery store has Tombstone frozen pizza, chicken nuggets, bagels, lunchables, Uncrustables, easy to make mac and cheese, microwave foods, etc. Not too much to pick from, but you won't starve. If you don't have a 1 bedroom villa, you won't have an oven, so keep that in mind.
Disney Springs has lots of choices. You can't go wrong there. It is about a 30 minute bus ride from AKL.