At Hollywood Studios you're on one of the two patios at the back of the amphitheater. There's a $750 food and beverage minimum.
In Epcot you pay a site fee ($250-$575, depending on location) and then a minimum of $22 per person for food and beverage. There's also a $75 setup fee for any location but Upper UK.
Both parks have a $12.95/pp viewing fee for any guest who doesn't have park admission, and both require you to charter transportation for your guests (there are a few exceptions at Epcot - you can walk in to some of the venues, like France and UK).