There is no bus service from any of the Epcot resorts (Boardwalk, Yacht Club, Beach Club, Swan and Dolphin) to Epcot. Boat service is available via the Friendship boats that travel between the Epcot International Gateway and the Disney Studios. The boats make three stops along the route at the Epcot resorts. Most people just walk to and from Epcot from this area since it is so close.
The International Gateway has the same hours as the Epcot main entrance. If you do this on a non-EMH evening this entrance will be closed when Illuminations ends, around 9:20pm or so. This would be easier to do if you pick an EMH night for either Epcot or the Studios. You can easily get to the Epcot resort area from either park. If driving you should park at the theme park closing at the latest time. If using Disney transportation you can get a bus back to your resort from either park.
I just noticed that your meal in WS is around 8:00 pm. If it is not an EMH night you will not have any time to exit the International Gateway and return since the park will surely be closed by that time.