I would say you at least need to have an idea of when these characters start meeting, and when the best time to get in line is. All of them tend to have longer lines, especially Jack and Sally. Otherwise you may spend most of your time waiting in character lines. Once you do J&S and Moana, you should easily be able to do the rest. The great thing is, this thread is the best place to get all of this information! It was the only reason I even knew that Jack & Sally had switched locations last year, and that I needed to get in line ASAP for them. We were done with them before the party even started!
I'm doing a loose plan this year for our party. We are surprising my DD9 with this trip, so I'm not able to ask her what she wants to do ahead of time. We did J&S and 7dwarfs last year, but had to leave Moana's line for a potty emergency
so I'm thinking we'll see her. We're also doing the Dessert party. My fiance has never been to the Halloween party, but he's very go with the flow. His only request was the dessert party! We did that on our last trip for HEA and he hasn't stopped talking about it! We'll are also using this as our only MK day of our trip so we'll be doing rides during the day.
I haven't heard a lot of reports about the Descendants dance party. Did anyone stop by that who went to the first party? My DD9 is a HUGE Descendants fan so I think we'll want to stop by there.