If the restaurants won't (or can't) split the tab, I suggest that you each take a meal. It should even out, but may not. How "picky" you want to be depends upon everyone in your party. Some restaurants are a lot more expensive than others.
The other alternative (which, after a bad experience, I 've been known to use) is to bring a notebook and calculator. Either let one person be in charge, or pass the notebook down, and write down the item and price AS IT'S BEING ORDERED! Don't forget drinks, coffee, dessert, etc...some restaurants charge for refills, some don't. (It's amazing how many people can't remember the price of what they've ordered....and very few guess a "higher" number!
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Also, make sure you ask what the local tax is, and everyone should agree on what percentage tip should be left. If I'm embarassed by someone else's idea of adequate, I always throw in a little extra in mine.
Again, one person will be responsible for paying the tab. As long as everyone knows this in advance...and they bring cash...it will work fine. (WDW has many ATMs in the parks.)
I'm not terribly fussy about this...as long as someone is "in the ballpark" I don't worry about every penny...if I like them enough to vacation with them, I don't mind "treating" a little, even if it wasn't my intention.