I was just about to say this! I love doing this and then going out to the observation deck for the fireworks.The lounge at the top of contemporary if you can get in. Not the lowest cost place to do this but it's a great view and something you should experience at least once. Aim near fireworks at MK time great view of them as well.
I enjoy having a drink pretty much anywhere along the lagoon in WS.The Polynesian is nice if you like Dole Whips--get the Spiky Pineapple and sit on the deck to watch the fireworks. Not as good a view as the Contemporary, but the drink is pretty amazing and it probably won't be as busy.