I've been on one second look already, with 2 more to follow, and all of them asked me in an e-mail to please bring a white coat. On the one I went to already, another girl showed up in a full suit with an attache case for a second look and she kept being confused with the actual interviewees that were there for the day. She looked very professional, though, but I think the PD and staff seemed surprised when they met her - I think they were expecting business casual and a white coat?
Hope this helps... and I don't think this question is stupid to ask programs. I doubt any program coordinator/secretary is going to run to her PD after you ask her and say, "WOW Joe Shmoe called to ask what to wear on his second look here. I bet he kills 5 patients on his first day as an intern, what an idiot!"
Good luck with your second looks and good luck in the match as well.