Hi Jennifer:
Weather in October generally hovers in the mid-to-high 70's, and hurricane season, which starts in the summer, tends to taper off by October. Keep in mind that while the weather can get crisp in late October, it's usually not too cold, and Disney resort and waterpark pools are heated all year long. Given that weather can get crisp, I would make sure you bring layers of clothing since it could be comfortably hot or warm during the day, then be crisp at night or the following day. So make sure you have some long sleeved clothing or jacket as well as long pants.
If your question about dress concerns dining and not weather, dining at Disney World is a casual experience, so in general, a decent tee-shirt and pair of shorts will suffice. You can wear casual clothes to dinner shows as well. If you are dining at one of Disney's fancier signature dining restaurants, men are encouraged to wear khakis, slacks, jeans, dress shorts, collared shirts. Sport coats are optional while women can wear capris, skirts, dresses, jeans, and dress shorts. Children tend to get more leeway.
As for special experiences, you'll be at Disney World for
Mickey's Not So Scary Halloween Party, a separate ticket event in the Magic Kingdom the features trick-or-treating, character experiences, a parade, and more. Also consider checking out the
Epcot Food & Wine Festival where you can drop by food and drink kiosks around Epcot's World Showcase to experience flavors from around the world.
Enjoy your vacation.