what a predicament. I'm assuming he's using the word lolita which no matter what some people may argue does NOT describe legal aged teens.
I don't think anyone here can telll you what to do, in the end it'll be your morals that come into play here...nor ours.
However if it were me, I'd have reservations having my name attached to that banner even if I didn't create it.
People who know you designed the site may assume you designed the banners.