They haven't announced specific dates yet as far as I've seen.
To get an idea...last years frozen fireworks were only shown Sept 5th-Sept 28th and were only on Friday, Saturday, and Sunday and at 9:45pm
So for this year I imagine it would be about the same. The fireworks won't be shown for the entire summer frozen event and only be on the weekends. Of course it could very well change. However I don't see them having Fantasmic and Frozen fireworks every single night for the length of the event.