I believe the Friday night EMH is Animal Kingdom, open until 8pm.
On 9/15, MK was pretty empty in the afternoon runup to
MNSSHP. We hopped over from Epcot around 2pm, and everything, and I do mean EVERYTHING, that we attempted to ride was walk-on. We even had our own log on Splash Mountain.
We didn't do many rides after the party started, but I was really suprised how dead the park was in the afternoon. For some reason, I thought it would be more crowded than normal. I didn't really notice much of a crowd until after the party had started.