Have you visited Florida, or WDW before? Generally speaking, you will only find a firm dress code that requires gentlemen to wear jackets (and ties) at very upscale restaurants or clubs. At WDW, the only onsite restaurant that requires men to wear jackets is Victoria and Albert's at the Grand Floridian. At the other "signature restaurants", business casual is accepted--the Disney definition of business casual is very liberal (no cut-offs, no t-shirts with objectionable printing, etc.).