I know that 2 years ago, we were at WDW for 4th of July--I remember they were launching fireworks from all of the different lands (we weren't in the park but remember a CM telling us something to this effect) and also from that little island (or a barge if there isn't an island) in front of the lagoon. Also, the Californian Grill actually is only available for a special (and pricey) price fixe meal--would have cost us about as much as to eat at Victoria and Albert's but with that awesome view of the fireworks. We actually watched under the monorail track in front of MK...let's just say, aside from the noise--I could have read a book as it was so bright.
Get there early that day if you are not staying on sight--Magic Kingdom has been known to reach capacity (for off-site and day guests in any case).