Hi
Can't share any info on the deluxe rooms as I've never stayed in one, but have been to WL 5 times with kids from 5 months up to 5 years.....
They sell diapers at the Mercantile, however they are small packs of 8 or 10 for about $7. I'd imagine they have a very limited amout of jarred food in a pinch. When we travel with the little ones, I bubble wrap all of my jarred food, planning for each day so I don't have much leftover. Then I ship a box about a week before that contains all of my baby items that won't be coming home: food, dipaers, snacks for the toddler, wipes, disposable bibs, disposable changing pads, etc. It will be waiting for you when you get there and you won't have to lug a big heavy box through the airport. I am assuming you are not renting a car. If you are you can go to the grocery store when you get there to purchase these items. Also if you use Tiffany Towncar service for your transfer, they will provide a half hour grocery stop. We have done all of the above.
As far as the ages go, I've done it a bunch of times, just take it slow, return to hotel in the afternoon for naps, and have a great time....
I'd highly recommend bringing a double stroller, or at least a stroller for each. My DD was 2.5 on our first trip and we used the stroller everywhere we went, even around the resort. Also a snugli or sling for the baby is a must for waiting in lines, etc....
Have a great time!