Wow fireworks get cancelled in the summer?? I would think they would be fine but I guess if for some reason it's windy I can see it happening. One night when we went in March it was super windy and they announced they may be cancelled but sure enough they weren't I love them with the music it's just amazing. Thanks for the input!
There can be a lot of wind in the summer, or at least June, and definitely also in November.
June 2009 over a 3-night period, they stopped the fireworks mid-way through the show one night, and Tink and Dumbo didn't fly that night, or the night after. Only the third night (and maybe the night after that) did fireworks run fully with all effects. Unfortunately, fireworks are always luck of the draw--you can wait an hour or more for the show, only to have it canceled or abbreviated.
If you don't mind seeing the fireworks from the Rivers of America, then I'd do the Fantamsic! viewing on Night 1 and just stay to watch them after your Fantasmic! viewing. For kids your age that might be better than the castle anyway, because they'll have a mostly clear view. I'd then see WoC on Night 2, and then try casually to see the fireworks on your last night.
If you must see the fireworks from the castle, though...then I do still agree with the "see fireworks as soon as possible" rule (provided they're a high priority). However, if you only have 3 days, and you can really only do one nighttime entertainment option a night (including castle fireworks), then there's no real point in seeing fireworks first, as you'll only have one try at them anyway.
In that case, are there any days you're going that are more or less crowded? (For instance, a Friday or Sunday night is usually more crowded than a Wednesday night.) So if castle fireworks are a priority then all other things being equal, I'd probably do:
*Lowest crowds day - Fireworks (as you have to get there early to get a good position)
*Next lowest crowds day - World of Color (you'll have a Fastpass and they haven't been overcrowding the viewing areas, but lighter crowds might be a good thing)
*Busiest day - Fantasmic! (with your dessert package it won't really matter how crowded the parks are)
But it may not make that big of a difference any way, so do as you like.
Have a great trip!
