So I called HT today and this is how they are answering, "Thank you for calling HT. Pre-order you Twilight DVD and receive an exclusive invitation to our DVD release party. How can I help you?"
You can preorder your DVD in the HT stores starting tomorrow. According to the gentleman I spoke to, when you preorder in the store, you get your invitation to the release party. He said the party is limited to those who have preordered their video, and you need an invitation to come in. The party is from 9pm-1am and there will be games and prizes.
I asked him about those people that have already ordered online, and he said they should let you in with your email confirmation. But he didn't sound too confident about that and mentioned they are still working out details. So I would recommend calling to see how your local HT is handling it.