Best bet is to call guest services at Epcot and ask. While someone here may have some idea of how it worked previously, who knows what changes were made this year. They should have very specific information available to tell you exactly where to go. As someone who has traveled pretty extensively at WDW with someone in a wheelchair, I can tell you that they certainly have either thought of this, or if you bring it to their attention will make sure you are accommodated (although you don't need to, I've found it's good to note on any reservation for food, etc. at WDW to expect a guest with a wheelchair, as they can make sure they have a more ideal spot and don't have to scramble at the last minute).
Have a great time!
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