Wishes is definitely happening during your vacation. Perhaps you're not looking in the right place to find the schedule. To get to the parade and fireworks schedule, your first step is to go to the Magic Kingdom park calendar for September, found
HERE on the WDW website. From there, you'll click on the schedule inside each of the calendar boxes. For example, clicking on September 2, will bring you to
THIS detail page where you can see that Wishes is being shown that day at 9:00 p.m.
In fact, the only day that Wishes will not be shown during you trip is September 4. This is the first night of Mickey's Not So Scary Halloween Party. If you go to the party, you'll be able to see HalloWishes, the special Halloween version of the fireworks.
Have a great time at Walt Disney World.