Hi Valerie!
It sounds like you're in for a fun vacation! The Polynesian is a great resort!
Extra Magic Hours are a perk to guests of the Walt Disney World resorts. There is not a charge for this. Personally, I think this is one of the best benefits to staying at the resort. I love having extra hours at the parks every day!
Typically, some of the park's show schedules are available on the Hollywood Studios' calendar page. For example, looking at
August 27th you can find the times for the Beauty & the Beast show, the parade and Fantasmic! Unfortunately this does not include the smaller show events or shows like Lights, Motor, Action or the Indiana Jones Stunt Spectacular. For those, you will have to wait until that day to see the full schedule.
Hope you have a great trip!