It took me 26 minutes on the phone to a Chicago phone number, but I finally got two linked reservations for the Resort. First two days at the BotCon rate US$114, and the last five days at the regular rate US$129. (all plus $70 resort fee and Tax)
One thing that doesn't make sense on their reservations site is the "buy 2 get 1 free" deal. If that means the standard rate of US$129 is free for every third day, that would equate to US$86 per night... but each time I tried adding days on the website, it would keep charging the full rate, and there was no option before filling out the payment details to add the free rooms on.
EDIT - I did a new reservation, at the full rate for the seven days, and selected the "3rd day free" deal, and all it says in the email is "discount applied after second night".
So, it looks like you check-in, they put a hold on the full amount on your card when they swipe it, and then after the second paid night, your bill gets credited with a free night.
Why can't they just give you the discounted total in the email confirmation... so I have no idea how much it will all cost after tax, and after resort fees (which they'd still charge for the free days). In other words, I have no idea which reservation will work out cheaper, in order to make sure I cancel the right one.
