We did a sold out Christmas party last year December 2014 on a Tuesday the week before Christmas week. It was far too crowded for my taste, and if I'm the major planner and decision maker I don't think I would do it again. // Do note that we were there mostly to do rides, but wanted to do three other events too -- Anna and Elsa (double dip crowds for that -- day guests and party people). We also wanted to see fireworks and a parade, so were planning on the second one. // The people who seem to really enjoy the parties most are those that are into the characters, as there are lots of those who you don't see regularly, so if that's your thing, you might really enjoy the party for that.
Anna and Elsa -- waiting by the castle for that was like being packed in like sardines. Crazy -- and then a 40 minute line at Casey's afterwards to grab a hot dog. We were very fortunate to have one person in our party grab an outside table, so we had a place to sit.
Before Anna and Else, we thought we'd check to see if we could get 7DMT in, but posted wait time, probably exaggerated was 1 hour and 15 minutes, which wouldn't have been good for seeing the show, so we skipped that. My mom and I scoped out a place for Anna and Elsa, and my son and my nephew went over to Big Thunder Mountain and Splash Mountain and found those lines quite manageable.
OK we thought -- now people will get getting ready for the first parade, so this would be a great time for lines, right? We headed over to 7DMT again -- still posted times of an hour and 15 minutes -- too long for us. So we did stuff with shorter waits, Mickey's Philharmagic, Small World, and Peter Pan (The first two were practically walk on, but I wouldn't be surprised if our wait for Peter Pan was almost 25 minutes.) Timing now is such that we should really scope out a spot fairly soon for the second parade and fireworks, which we did want to see, so we headed over to Frontier Land, as crowds are typically more manageable for parades there than Main Street. We did Haunted Mansion and Pirates with lines of maybe 20 minutes -- not all that bad. // We got a spot for the parade 10 minutes before it started. And it was awfully packed crowd wise for that. We were in a walkway area that they had closed off for people till 15 minutes before. And we saw parade and fireworks just fine. I'm not really a parade or fireworks person, but most people rave about these at the parties.
So now it's 11 p.m. and we say, we want to try the new ride 7DMT so head over for a third time. We are a little disappointed though as we doubt we'll be able to get both 7DMT and Space Mountain in (the two remaining things on our hope to do list). Line is now posted as 45 minutes and we go for it. It only take 35 minutes though, so after that we jog over to Space Mountain and are able to get two rides in before midnight. A 10 minute wait for the first ride and walk on for the second, and we board at 11:58 p.m. for that second ride.
We like to do some main street USA hanging around and shopping too so start that at 12:15 a.m. Stores have plenty of people (so it feels busy, but not the overwhelming crowdedness before midnight that there was everywhere). We look around and shop till about 1:30 a.m. By then (we are staying offsite), it's actually pretty easy to navigate the parking lots, and there are still plenty of people but no big traffic jams and waits, and we are back to our offsite condo by 2 a.m. // It's a short night for us as we do rope drop the next day for our one day at Universal with a park to park pass.
I think next time I do the MK, I'd rather do rope drop than party. Actually though my next time at the MK which won't be till March of 2017, I'm going to do the Keys to the Kingdom tour and then hit attractions after that. Hopefully I'll be able to get a few fast passes as line predictions without those late afternoon and evening during spring break look insane. And one one hour line is all I'm up for. After that for a favorite, I want line of 30 minutes or less. If they are longer than that, I'd just prefer to skip things entirely.
All in all we had a good time. My favorite parts were relaxing and eating at Casey's after the insane crowds for Anna and Elsa, doing Mickey's Philharmagic and Small World with short lines, and shopping on Mainstreet USA after the majority of the crowds had left. The special Christmas stuff, because of the crazy crowds, just didn't cut it for me. And although we did stop three times for the freebie hot chocolate and cookies as my nephew in particular liked doing this, I wasn't impressed and could have skipped that.
Anyway this is one person's detailed perspective (mine) of a
MVMCP sold out party day. Oh and I've been do the MK on crowd calendar 9 and 10 days before, so FYI, please note that the crowds are not anywhere near those levels. The party was kind of like a 7 day for me, but a 7 day without those first two hours after rope drop, which are heavenly and you don't get with a late afternoon event.
There's been some good advice given in this thread...........no matter what happens I hope you have low crowds and a wonderful time. 
