When I went on an Illuminations cruise, the driver offered to drop us off at the International Gateway so that we could go back into Epcot, and walk back to the buses. I figured it would be a pain walking against the traffic of the people leaving Epcot, and then having to walk through Epcot to get to the buses. I wound up taking a cab back to the Port Orleans French Quarter. We had a very tired six year old with us, and I don't think he could have made it all the way to the buses. But, it was good to know it would be an option.
Take a cab. It's definitely better than walking back through Epcot, and waiting in a line to get on a bus.
Karen