Hi Mandee,
I love Disney in October! With Mickey's Not So Scary Halloween Party and Epcot's International Food and Wine Festival, it really is a great way to spend the weekend!
I would go to EPCOT on Friday. You will need fresh legs and all day this park. Plus the World Showcase will be packed Saturday and Sunday with locals who want to enjoy the Food and Wine Festival. Saturday could be spent at Magic Kingdom or Disney's Hollywood Studios. Animal Kingdom, if you are going, closes early so you could either head back to Epcot or Magic Kingdom. The last day you could split between your two favorite parks.
Mickey's Not So Scary Halloween is a great way to enjoy Magic Kingdom. There is lots of candy to be found and the lines are shorter. In addition, the characters are dressed in costume and the parade is my favorite! There is an additional fee for this party but my family loves to get dressed up and tour Magic Kingdom. It is a nice bonus for a trip. However, if you are on a budget or it is your first trip, you may want to save this experience for another time.
Wishing you a magical vacation!
Beth