This seems to me to be more of a sad situation than a dangerous one. I think relationships formed in nursing homes are not unusual, but when they're unwanted or with the help, someone should step in. You should speak to the waiter about this, tell him the situation and how uncomfortable you are with this, or have the manager speak to him if you're reluctant to.

My "problem" is that my husband, who has Alzheimer's, lives at home with me, and is still highly functional, wants more sexual activity than I do at this point. I feel bad and he's frustrated and sad, but we're just not in the same place where we used to be. I try to gently explain that I'm old and not feeling it anymore, but he can't let it go. I don't want to hurt his feelings, but I don't want what I don't want either. I end up feeling both put-upon and guilty.