Everyone's system and routine is different. That being said, having dinner at 4pm and then not eating again until possibly midnight is a long stretch. In reality you will be doing almost 10K--5K as a race and 5K as a scavenger hunt. I would use the same suggestions and tips as I would for a longer distance event. "Don't try new things on race day. 5K isn't a terribly long distance, but if you are wearing brand new shoes for the event because they look nice and you get blisters or they rub your feet raw, you'll be miserable. Same goes with a costume. Giant Mickey hands and ear are a cute costume; but, will you be saying that after the race? "Don't eat too out of your 'zone'. If you are used to eating an hour before you go out for a run, try to stick close to your schedule. Also on race day, try to eat familiar foods, or food that will not upset your stomach. I eat Thai food regularly before I run. If I eat oatmeal or yogurt, I end up heaving on the side of the road after a couple miles. "Remember to refuel. Stay hydrated and rebuild your nutrients your used during the race. I want to say Restrauntasaurus was open after the race last year? I ate my banana and drank my water and rode Kali River Rapids four times to cool off. It was HOT. If a restaurant accepts the dining plan during normal park hours, it should accept it after park hours for a Disney event/party.