I would consider using a taxi service to run out after getting settled, or a town car from the airport, with a quick stop at the grocery on the way. I think either would be cheaper than the $50. I know most resorts sell bread and milk in their little grocery section which are a little more, but not outrageous. Last option I would suggest is pack an extra suitcase with a case of water in it, check it on the plane. Then you have a spot for souvies to go home. Not as practical... but the cheapest solution.
A taxi would have to run AT LEAST $30 including tip for round trip. $30 plus the groceries will easily add up to $50.
A town car? That's going to run about $60 including tip for one way from MCO to the resort. Plus, if you're staying at a WDW resort, you can take DME for free. I can't see paying $60 for a ride PLUS the cost of groceries in order to save LESS than $60 on the cost of the groceries.
The other commodity is TIME. Stopping at a store, or taking a taxi to and from a store, uses up valuable vacation time. With both Garden Grocer and Gooding's, you don't have to be present for your delivery, so you don't even have to waste time waiting around for it.
And about it perhaps being cheaper to buy breakfast at the resort versus getting the delivery. Maybe. Depends how you'll eat. But then there's also the time and convenience factor. We prefer to have breakfast foods in our room not so much for the cost savings (although that makes it that much more attractive!) but for the time savings and the convenience. Instead of getting everyone ready and marching to the food court and then spending time sitting there eating, we typically eat vacation breakfasts in the tired-and-comfy time between waking up and leaving for a park. Also, one child can eat at a different time from another (due to sleeping late, or lack of interest at the same time, etc.) rather than making everyone be on the same schedule. Same for the parents. I'm usually awake earlier than everyone, but if I don't feel like leaving the room to go to the food court I can stay snug in our room but eat my breakfast while everyone is still asleep. Then when everyone gets up, I can get the kids ready in the morning while my wife can relax and have her breakfast.
In addition, we happen not to be big "breakfast food" people. Bacon and eggs and potatoes? Waffles/pancakes? Yeh, sure, but we tend to enjoy cold cereal and milk, bagels and [insert preferred spread here], yogurt, cheese sticks, fresh fruit (like bananas or grapes). it's very convenient for us to have that kind of stuff in the room with us.
For savings and for food preferences and for time savings, breakfast in the room is perfect for my family, so for us the grocery delivery is a no-brainer.
HAVE FUN!!!