We were there two weeks ago and had a PS for 12. Next to us, there was a family of 20. I believe they had to put two long tables together for them and two people sat on the ends, right in front of the fire pit.
The adults will love the food and the kids will love all the activities. They have coconut races and h-hoop contest every hours, about 30 minutes apart. Bring your video camera and relax.
PS exactly on your 90 day mark with that many people. And depending on your travel dates, you might even be able to see the Wishes from your table.