I will give a "chalk talk" at the outset, but if everyone has studied either a book or an on-line tutorial, or even just looked at the standard Points-of-sail circular diagram, I can make the talk-time shorter and sailing time longer.
But I do not assume anyone has read or studied anything, I'll ask them, and ask about any prior sailing experience no matter how long ago.
I think the bigger question here is about learning styles and how they mesh with teaching styles. I tend to think sailors learn better by sailing, then looking afterward to see how "the book is right", than reading the book and comparing their experience to it--almost too much to think about when it's all new. So I'm more likely to give a short "debrief" with (my beat-up) book afterward if they have time, showing them how much of the book they just did. I think it leaves them on a high note.
I could be wrong doing "do, then read about it", if someone's learning style is the opposite, but haven't seen a downside in actual practice.
Reading beforehand is fine, just don't let it make you nervous or intimidated. Sailing is easier than you will expect..
That all sounds excellent. Sounds like I'm letting my excitement get out of hand. :-)