Just have your confirmation number available in case your name is not listed or listed properly on the list the Cast Members have at the park entrance.
There are many breakfasts inside the parks before opening so don't worry about it.
They have one line open for Princess Breakfast guests only. You have to give them your last name and confirmation number. They will only let in the number of guests your party has reserved. It was really peaceful walking through Epcot without crowds. You can even hear the music playing in the background. My husband and DS met us later after the park officially opened.