I haven't run this by anyone at my library yet, but it sounds like a good idea. Sami from the Sprylibrarian wrote about her library's Big Brain Bash event recently. I asked her for the materials, and this morning I had a big, wonderful e-mail telling more about the event and the various Word and PDF documents associated with it. I am so excited to pitch this to our director and other librarians.
We have two big outreach events at our library, but both are in the fall. Harry Potter Night will take place on October 24, that's as close as we can get to Halloween this year because the 31st is Long Weekend and we won't have any students that day! The other big event is Snowden 'til 2. This takes place the last day of class, and runs from 9 p.m. until 2 a.m. (hence the name). Professors come give review sessions while we order enormous sheet pizzas, serve cookies and coffee, hire professional massuses, coordinate video games on projectors, Play-Doah smashing, and pictures with Santa. This draws 400+ students on a campus of 1,400.
Perhaps there is enough in the spring to draw their attention... spring is so busy, and I get the impression that students don't take anything as seriously that semester as they do in the fall. But this event seems labor-intensive, but inexpensive, and if it was successful there, then it should be successful here.