We’ve done Instacart our last two trips and had good luck. Both times we scheduled the delivery for when we were back at the resort the first night around dinner time, and I met the delivery person (can’t remember if that was a requirement with Instacart or not, but I do know I had to show ID because I ordered some beer). We placed the order only and hour or two before the delivery time - the times available were not that far off. I was texted when the person began their shopping, and I was also texted during the shopping about something that was not available/different and asked about a substitution. Then they texted/called when they arrived and I met them out by valet. The first time she carried some of the stuff in with me to where we were sitting eating dinner at quick service. The second time they had put everything on a luggage cart, so I just wheeled that in (we were at a table service dinner right in the lobby area) and bell services let me leave the cart over with them.
We ordered our food from Publix - you have a few different choices with Instacart. Whole Foods would normally have been our choice, but they don’t have beer. (Not to sound like a lush - we had balconies both times and our kids are little, so a big part of going Deluxe - Polynesian first, Wilderness second - was having the balcony to sit out on and decompress while the kids were sleeping. Considering a six pack was about the same price as a single beer at the hotel, that saved some money.)
Also, if you want to look, TouringPlans Blog did some side-by-side comparisons last summer of some of the grocery delivery services, largely comparing prices. It was interesting (can’t remember when it was exactly, but I know it was in the lead-up to our August trip last year).
