I know that DC had asked about the Hyatt's cancellation policy. I emailed the woman I've been working with, and here is her reply:

>>We have a 24 hour cancellation policy. Please just let him know to cancel within 24 hours of his arrival date. Once we set up your block after we receive your contract your guests can call our reservation number and say they are with the Small Reunion (or what ever name you choose to put it under), please just make sure they do not book on Hyatt.com as this is not refundable.<<

So, if you were planning on booking for Friday and Saturday, you would have to cancel no later than Thursday.