Hi Elle's,
Oh my. Awkward. Small group dynamics. But you're the one who knows them. And I suspect that most of them (as "cool" and maybe socially awkward with women) will end up being ok with someone who is seen to be "sure of themselves". I mean there will be a weird period of adjustment, but ultimately they will settle back into the "usual" routine.
So how to start a change in dynamics? I might start by casually asking slightly edgy things, like "hey, did any of you ever wear your sister's panties?". I suspect that in a group of 5 guys, 2 probably did. And liked it.
Then, if someone owes up, you can say something like "you know its weird, but I still do that sometimes when I go to bed. You know, its sort of fun?)
Well, once a discussion of wearing the other gender's clothing has started, you can lead the discussion where you will with subtle comments.
Don't know if this approach would work for you or not, but its a suggestion.
Carolina