Let's party !: ways to interact with the students similar to "Science Meets Speed Dating"
Great idea, given that many students have no idea what scientists actually do (and some confuse scientists with full-time teachers; not sure what your students think -- that would be interesting to know in advance to address these misconceptions and to reinforce what is true). And even better to go beyond a simple poster session or the like.

But what exactly should the students take away from the event/this experience? For example,


that science is a weird mixture of great fun (doing something new) to excruciating agony (getting papers/proposals rejected, non-significant results)? Then I'd second a science slam. If you have good speakers who are willing to be open about their success and failures. Personally, I'd go by something "behind the scenes" like. A couple of placed cameras with a fast forward montage of a typical day might be interesting (explaining what you do in the video). And plan some time for questions.
to show specifically what your institution researches? How about something hands-on? Something that shows the progress, not the end result that ends up in papers or text books?


Just, whatever you do, I doubt that anything involving speed would get the message across. Perhaps it's my aversion to speed dating speaking here, but in the end it's all a blur and I wonder whether that fits your goals. I think identifying the misconceptions and specifically replacing them with what you actually do is the way to go, rather than just short and diverse contact that likely will remain superficial.