You'll be surprised. Park is not super packed Memorial Day weekend. It's our 4th year in a row to plan to be there that weekend. While it's a Holiday and they are always somewhat more crowded than a non Holiday weekend, as Holiday's go, it's one of the lower crowded ones because you have the Northern half (roughly) of the country still in school and too close to the end of the school to take a vacation to Disney. It's sort of similar to Labor Day and how you have most of the Southern half of the country in school and too close to the start of school for them to take vacation.
Anyway, we have watched fireworks from Narcoosees (one of the last performances of Wishes actually) last year and it was good. Nice view. They let folks out on the patio, pipe in music, etc. You'll loose all the projections of course. But with an AP, you'll obviously have many other times to see it that way. So I'd say, stay at Narcoosees and watch. Get a different perspective