Its not hard at all, you call the dinning reservation number and tell them you are making reservations for a group and they will connect you to group dinning. You will make your reservations through them.
My family is going as a Grand Gathering 10/24-10/27. There are 25 of us. I called the first day I could & Chef Mickeys said they could only get us all in at 7am. 1900 Park Fare said they could only get us all in at 8pm. Crystal Palace was the only one who would give us a breakfast ADR for 8:15am. They also said they couldn't guarantee that we'd all be sitting together at any of the resteraunts. That was very disappointing. I can only hope that if we can't all sit together they don't automatically add the 18% gratuity for the buffets. Good Luck!