My wife and I have run W&D the last two years. As others have noted, the first year the after-party was a fiasco. To sum it up, it was just too many people crammed into WS. Yes, I realize WS should be able to hold a lot of people, but that was the busiest I have ever seen it.
Last year was MUCH better. I don't know if they limited the number of tickets or what, but there seemed to be much more space to get around and the lines for food did not seem nearly as long as the first year. Probably less crowded and shorter lines than a typical weekend evening during F&W, so if you want to try the F&W kiosks, this is a great time to do it. As for rides, I know they had Soarin' open, and a few others (I think M:S and Maelstrom, and probably a couple more). We were able to walk right on to Soarin'. We probably could have ridden it for two hours straight without ever having to wait. I imagine most of the other rides were the same. It seemed like most of the attendees were focused on the food and drinks, so the rides were pretty empty. You said you don't care about meet n greets, but the usual WS characters are out. I specifically remember Aladdin and Jasmine in Morocco and Belle in France. I think there were no lines at either one.
For a more detailed description of the after-party, check out my wife's blog. The discussion of the after-party starts about 2/3 of the way down the page.
http://www.runningonwaffles.com/2011/10/10/marathon-mondays-wine-dine-half-marathon-recap/
Just a note, the race finishes outside of Epcot, and the runners do not enter until after they have finished. So if you are wanting to see your sister and her fiance actually run, I don't think you can do that from the after-party. But it's definitely a great chance to celebrate with them after! Maybe someone else has experience with watching the race and can chime in on good viewing locations...