Gotta love Disney! I used to perform at Epcot.. it's an awesome place. Although, I frequent Universal Studios. Gotta have the annual pass if you live in FL.
For Halloween stuff, there is always Spirit Halloween as Victor-eyd recommended. Unfortunately, the Halloween stores here are all seasonal. There was a Halloween Express store on Sand Lake Road in Orlando, directly across from the Florida Mall this past year. But I believe that was seasonal too.
For attractions on a side note, Skull Kingdom on International Drive is open all year round.
http://www.skullkingdom.com/
Happy vacationing!