SECOND UPDATE: Just got back from five days in the parks. Exhausted (and experiencing a little post-disney depression) but still very satisfied with how the whole trip went!
MK on the 31st was extremely crowded (more so in the latter half of the day) but surprisingly manageable - we got there at like 7:30am and made a beeline for the Mine Train at rope drop, boarded in 25 mins no problem. The rest of the day was similar - I don't think we waited in any line for over an hour despite the immense crowds. As the park filled up more with new years crowds the lines obviously got longer; SGE had a 50 minute wait at one point, amazingly - we wouldn't have even thought to look in its direction let alone consider going on it, but my siblings heard it was closing and they got nostalgic so we went on TWICE. I won't miss that ride but I will but I won't etc. Sad to see it go despite my feelings about it.
At around 8pm we staked out our spot for midnight fireworks in front of the castle. The entire area - the hub and its surroundings, all of Main Street - was so unbelievably crowded, so densely populated, it made the most packed concerts I've ever been to seem like rundown bowling alleys on monday afternoons. My god. It took me half an hour to get from the Walt and Mickey statue to Casey's. I don't think I ever want to do MK on NYE again, but I'm glad I got to experience it. I'm not big on fireworks or huge crowded celebrations but this was pretty great.
AK was rainy and a bit chilly but obviously much less crowded than MK was the previous night, which made for a relaxing, laid-back day - FoP left me completely stunned, great ride. For what it is, I admired the River Journey too, despite it feeling a little bit too much like kayaking through a flooded Rainforest Cafe. The shaman was working.
The next day was Epcot; as for the whole drinking around the world thing, thanks so much for the advice, everyone - I didn't have any issues with sickness or anything, I paced myself, etc. I ate some fish and chips, some baklava, some egg rolls, drank a lot of water, made out perfectly fine (my wallet didn't though hahahahahaaaajajahaha i want to cry). Loved Germany's grapefruit beer and Japan's hot sake.
The remaining two days were spent revisiting Epcot and MK - Epcot day 2 was nice because i slowed down considerably in world showcase and spent much more time appreciating the details instead of rushing to complete the challenge. MK day 2 was nice because it was less crowded (we walked right on to splash and big thunder) but also heartbreaking - walking away from the castle and leaving MK on the last day of your vacation is much more emotional than leaving the other parks. Already mentally planning my next trip, probably when SWL opens.
tl;dr - i went to disney world and it was good lol