I would choose a nice restaurant at Epcot or the Boardwalk, then take a nice stroll down the International Gateway walk (It's incredibly beautiful at night, and usually very peaceful - not too crowded) ending up watching the Epcot Illuminations together. You can also consider one of the Illuminations cruises. If you want a more intimate setting for dinner try the French restaurant at Epcot, or if you want something more adventurous try the Moroccan or if you feel convivial try the Tepanyaki Dining Halls.
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