I asked him if he wanted to dress me for a little while.
This happened to me and my wife was present and it was a real good experience for all of us.
I wondered if my date judged me for not wearing a bra, and if it was obvious.
I sometimes end up refusing because I hate the optics of it: The men sit around drinking, while the women wash up.
However you would have treated Trevor and whatever you would have talked about with your wife before you saw this thing you were never supposed to see, do that.
Your obviously open minded to be discussing sex with your friend and your husband is up for it so go for it.