Unless they change things, the only time they have fireworks is when the park closes at 10pm. That runs thru the 3rd week of August.
We'll know what show to expect on Saturday March 31st when the park stays open until 10pm and spring break runs for 2 weeks. I think it will be the Aero 360 show at USF with nothing at IOA.
While you'll miss the fireworks show late August and September, the crowds are very light and that makes up for it. The walkways are less crowded, wait times for restaurants are reduced, and things are less hectic. People ask what to do since the parks close early. You go out to eat, or go swimming.