Wow.... Hopefully the floater won't ruin the moment... :P
Seriously, get creative. Or better yet, wait till marriage and do the right thing. I would be offended if I walked into a restroom with my children and two people were doing their business in there even closed door or not. I would probably ignore it... However at park bathrooms since they are dingy typically, I usually pay attention and recognize if there are other people in there. I probably would not call the cops if it was a concealed thing, but it may be "public ludeness" and please know, I typically don't call police for stuff.
If you are paying $40 each time, why not just get married and go into an efficiency together for probably not much more.

