We will have a party of 12 at SSR for Thanksgiving. No one's first trip, but we are the definite experts - being the hosts, we are also expecting them to look at us for the "what do we do now?" decisions. So we are pre-empting by planning ahead. If they want to do their own thing, they are more than welcome. We are using
DDP, and I made ADRs on the exact 180-day mark (with some changes since then

) - Dh and I organized a "dining rotation" so that we could eat with different family groups each day.
DH has also created an Amazing Race-ish "scavenger hunt," dividing us into teams and creating a fun, interactive game that will keep our focus from standing in lines and fighting crowds!
We are very excited - my parents have gone with us before, but never with my DB or DSis's families - this is our first time all together!
DSis went with her in-laws a few years ago and they had no idea what they were doing - it was the stereotypical "why do people DO this?" kind of trip. She is excited to go with US this time. And DH is a former CM, so he is always full of interesting tidbits about everything!
Good luck with your huge party! That is a LOT of people! I am just so thrilled to get to share my favorite place with the folks I love!