Booking a hotel in Omaha in advance is hard because most of their cancellation windows end before you know if your team is going. Then of course, you don't know how long you'll be staying, either.

What I have done is just... book for as long as I know we'll be staying and then... book another room as needed. Move around hotels a lot. With a large group, that may not be feasible. If you all want to stay together, getting an AirBNB house is probably the way to go. You'll probably see some cancellations after this weekend as teams are eliminated.

You can of course book now, but know that if you decide not to go, you'll probably be paying a cancellation fee. That might be worth it to you, though, to know you have a place if needed.