The Mad T Party is in "soft opening" right now only running on the weekends until June 15th. Last night was the first night that it ran and from the videos and reviews I have read, it looks like a lot of fun!
Earlier this week, Disney had all the times for the party on the website and they really were a mess. It was something like:
7:00-7:05
7:05-7:25
8:00-8:20
9:00-9:20
10:00-10:20 (when the park is open till 11)
All those times are now gone from the Disney site. Last night was really used to check how everything flows. From reviews I read, it seems like there was totally no crowd control going on because Disney was waiting to see how the crowds moved around the event before putting measures into place. Hopefully in the coming weeks they will update the times again.
However, the event runs ALL night. The times that were given seemed like the times the LIVE band were going to perform with the 7:00-7:05 being the opening event. When the band is gone, the DJ comes on stage to do his/her thing.
What WoC time are you seeing? If you are seeing the 10:15 show, you should have no problems being at the Mad T Party from 7 until about 9:15-9:30. The party starts each night 7pm and the live band performs for about 20 minutes each set. So, you would have to decide if you are seeing the 9:00pm WoC if you want to sneak over to the party for 45 minutes or so.