We were at WDW over July 4th last year and had a very hard time finding sweatshirts. (We needed two for our kids since I, thinking we won't need them in the summer, didn't pack any!!!) We checked the resort gift shops and park shops and found only T's. It was tough! FINALLY found them at the Rainforest Cafe gift shop.
My poor kids were freezing at Hoop-Dee-Doo. They did have jackets because it had rained, but the jackets were wet and no help at all. Our server was so nice though - he brought over two clean tablecloths for the girls to wear. They looked so funny with these big red cloths around their shoulders - but it did the trick until they warmed up a bit!