So...what do people do there when they are there for business, have only evenings free, and don't have park admission? Suggestions?? How's Pleasure Island now? Haven't been there in years.
Also, you can head to the Boardwalk and hit Jellyrolls, dueling pianos, and just absolutely great fun. There is Karaoke at the Swan Resort at 9:00pm in Kimono's, a bar with sushi.
Check your convention info to see if the "after 2:00 p.m. theme park admission tickets" are available. These are available to some convention groups and are good for attendees and their immediate family. If you can get them, Epcot is usually open to 9:00, so plan a visit there. Check the MK hours too. You might be able to enjoy an evening there.