Amy,
So here is what I think is going on. I looked at a few days in November. I saw Wishes listed for the 15th and 18th, but not the 16th and 17th. Coincidentally, the 16th and 17th are nights when the Magic Kingdom will host the
Mickey's Very Merry Christmas Party.
My guess is that for those nights you will still see Wishes being held, but a holiday theme "tweaked" version with a slightly different name (Holiday Wishes?). As such with a new name, it has not yet fed to the computer system.
Ultimately the only thing that matters is that I am sure they will have fireworks every night, and that you should be able to count on that. I would not worry about it if I were you, and I would just check the calendars over the next few months and the times should pop up.
Oh, and I am sure that all park guests will be able to see the fireworks on those nights, not just party attendees.
Have a magical vacation!