I was going to write something snarky about the bubble here, but after thinking about it, a half baked product of an all night hackathon getting angel investment is par for the course.

Definitely put the top ones on stage in front of investors, and, if you can, give every participant some kind of freebie(free pass to the conference?).

The people who participate in hackathons are exactly who you want to be putting in front of investors as much as possible.