I have found that sitting at a table trying to roleplay a festival or party can get a bit boring. Likely a failing on my part as the DM, but there it is.
The work around I tend to use is to actually throw a party. Recruit a bunch of your friends who are roleplay friendly, but not in the game, to play your important NPCs and then LARP it out.
Then again, I like throwing parties, so I may be a bit biased.