Just a warning if you have not done a party before, make sure you set your expectations. We've done it 3 times over the last 15 years, the latest being last month. It is over priced for what you get (surprise), but getting a reserved area to watch the fireworks is where you find the real value. Basically, you are paying for time, plus some desserts and a few drinks. You could camp out an hour or an hour and half before the fireworks start in a prime viewing place, or you could pay to attend the party, eat some sweets, drink a few glasses of wine, and then wonder over to your viewing area 10 to 15 minutes before the show starts. That's where you get a pretty good view (maybe not the best possible view, but not a bad view). Obviously, you could do the party afterwards too, but for us, at the end of the fireworks, we were ready to head back to the room.
I will tell a sad story about the party. My wife went to the rest room at our last party and ran into a woman that was crying. She was expecting a balcony view with staff service, first class service, and high end desserts. That's not what the party is, even if there are good options available. It's still basically a buffet of small desserts and a few free drink options. I get it, it isn't a cheap experience, but make sure you realize what your getting for it. Like I said, the reserved viewing location is probably the biggest value you're paying for.