Its an awesome event! Your ticket gets you in the gate at 3pm, and you have access to everything right off, with the normal day crowds. At 7 or 8 or whenever the parks close to day guests, only meetup folks will be in the parks. Trust me, its not a lot of people. Most everything is walk on, and sections of the park will be nearly deserted. Unlimited food opens an hour after park close, but they're giving out dining cards as well. You get this when you check in, and can use it anywhere the dining plan is accepted, up to park close. It includes a full meal, a snack, and a drink.The last time they did this, we ate early to avoid being starving when the free food opened. It worked out very well..
The free food is (or was) mostly buffet or cafeteria style, so it doesn't take long to get and eat.