Is there a major mall in East Fishkill?

No, unfortunately. Essentially all you have in this town are strip malls, like those you'd find in the center of Hopewell Junction. No major retailers that I can think of off the top of my head, either. There used to be a nearby mall in Fishkill, but that's all but dead. You'll have to head up to the Town of Poughkeepsie for the major malls, such as the Poughkeepsie Galleria, and I figure that'll take 20 minutes or so, depending on where you live in the town.