I'm excited by the possibilities and the interest everyone is expressing. However, I've been talking this over with the other organizers and the current consensus is that pulling off a full hackathon by the 27th is a little rushed. That said, I think this is a good thing for us to be involved in, and from the feedback I've gotten you do too. So instead we're planning on theming the HackerSpaceICR meetup on April 28th to be a pre-event for the Open Iowa hackathon (which will occur sometime in the next few months). Basically it'll be the same as our other events, show up and work on whatever, with the exception that a number of us will be working on finding data, cleaning it up, identifying people to collaborate with, selecting / creating a place to host the data, creating infrastructure for the actual event, going over what worked at Hack Omaha, etc.
We may have a company donating space, food, and wireless for us to use, so until we hear back on that the location isn't final, although it'll likely be in CR. Hours are determined by space as well, so nothing official there yet. I hope to have more for everyone soon.
-Mark