What to wear to "meet and greet"?

BLUF: What do I wear to an "informal session" that is "not an interview" with another finalist, meeting half hour with the other administrators and half hour with the tech department that I would theoretically lead? Suit and tie? Tie and blazer? I need to plan on introducing myself and give my vision for the tech department.

I am in the "last round" of the selection process after a phone interview, face to face interview with a committee of 10-12 people, and a presentation I had to come back and deliver to the same committee. I wore a gray suit and tie to the interview and blue suit and tie to the presentation. This job is for a Director of Technology for a much larger school district (4x bigger) than my current school district (where I serve as IT Director).

Also, somewhat related: Why are they doing this? Is it weird that they are bringing two finalists to this? Am I wrong that it is going to be awkward to see my competition? Why have all these interviews and presentations if this "informal meet and greet" can be a dealbreaker? I listed to MT and CT a lot, but I literally haven't interviewed in ten years. Finally, I do know they called my supervisor yesterday for a lengthy reference call, he told me. Is there anything I should be prepared for in a situation like this?

I am certainly interested in the job, as it will be a greater challenge than what I am doing now and the money will be anywhere from 25-40% more than I am making now but my commute will literally go from 5-10 minutes to 50 minutes one way (no traffic, rural). I am excited for a fresh start and new challenge after building up a great tech department where I am currently.

Thanks in advance!