Great question-the WDW fireworks are one of my favorite things and I would not want to miss them either. You did not mention when you were coming so it is hard to give an exact schedule but I can tell you that typically Illuminations at Epcot is shown at 9pm. There are occasional changes to this, for example, on Fridays through April 24, 2009, Illuminations is being presented at 8pm to allow for Extra Magic Hours. Other than that, it is usually pretty safe to plan on 9pm for Illuminations.
Wishes can be a bit trickier as the time for that show (which is AMAZING in my opinion) tends to move around a little more often depending on park hours, time of the year you are coming and if there are any special events going on that evening at Magic Kingdom. During the less crowded times of the year we have seen it at 7pm, however I have seen it as late as 11pm.
The best place to check for the exact times of both shows for your vacation period is at the Disney World calendar located
here . Depending on your vacation dates, the calendar may not be updated yet for that information so be sure to check back as your arrival approaches. Most of the time you will find you have plenty of time to enjoy your dinner and still make it back into the park to view these fantastic firework presentations. Hope you have a magical trip!