I booked my tickets through Get Away Today for our upcoming trip, and from what I understand, you should be able to pick up your tickets the night before with no trouble! The ticket stands are outside the parks, so you don't actually start using days on your ticket until you go through the gate Thursday morning. However, if you want to go into the parks that evening, you will need to add an extra day. The upside is that an extra day is very cheap, only like $10 per person. I'm thinking of doing that so I can see fireworks the first night.