If you are coming all that way, I would definitely spend $8.50 for the extra day, even if you don't use it. One option I wanted to mention though: if you love animals, you could just go to the Animal Kingdom Lodge (the hotel, not the park) to see their animals/savannas, that is free. It's really gorgeous.
Now that I think of it, I would suggest you do that. You could eat there, they have a food court area called Mara that is reasonable, if you are looking to save on food, or just go to see their animals.
We get annual passes for Disney (what can I say, we have a kid, we visit WDW a couple times a year) and that also offers us a deal for 20% off all food and drink card called the Disney Dining Experience. Doesn't sound like that will work for you, but it saves us a lot of money, especially because it includes alcohol. Nice discount for an expensive bottle of wine each night with dinner, lol. Basically pays the tip each night, can't beat that.
Have you looked into their dining plan? I have never used it, but some people like it. I think the best way to save money on food is to eat less of it, basically. Pack some snacks for your room, breakfast items, etc. I think folks save money doing that. We usually get a club level room and that includes a lot of food/drinks, so that sort of saves us $ even though it costs more for the room of course.
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