As Friday winds down, I will toss my thoughts into the frenzy that might follow.
The comments I am making are after reading from your workshop website. Since I am attending an event this weekend it will be interesting to see what comments are made the next two days.
I believe most guys who spend $400 for one day, are expecting more than just watching you shoot nude models. I can certainly understand your thoughts about standing around waiting, because I have done that.
Mose of the events I have attended have been "association" functions, such as the PPA or their affiliates. Those are mostly sitting and taking notes, but never nudes.. portrait, commercial, and wedding photography. However those events only range from $75 for a day or two, or in the case of a convention maybe $200 for 3 or 4 days on various subjects.
Some of the affiliated schools cost in the neighborhood of $400, but that is for 4 to 5 days of classroom instruction, and some allow shooting "samples" of the setups.. again not nude.
Since you are getting complaints, perhaps it is time to think about some separate time for those. But, I also understand the ramifications of that. Once a dear friend of mine, now deceased, would travel around with his young lovely wife as a model. He had a difficult time with the gawkers and wannabes who wanted to shoot .. shall I say.. unposed poses. Some that would cause embarrassment.
I once hosted Peter Gowland (long time ago), and we had a time for photographers to shoot models.. not nude, but lingerie, and all they had to do was send prints. I also hosted Steve Palen from Las Vegas, a prominent glamour photographer, and also asked for prints for models.
Both photographers told me I would probably get only 2 out of 10 photographers who would follow through, which was exactly right.
With all that said, only you can determine how to run your workshops, but I will pose (no pun intended) a question. If only you shoot and demonstrate lighting and posing techniques, and perhaps show how to select wardrobe, and maybe some props or backgrounds why is it even necessary to have nude models.
For the record, I am not being a prude.. nayyyy... I can photograph neeeked ladies all day long, but when you promote the workshop with this:
WARNING: This workshop may contain very explicit nudity. And show Penthouse models in all their glory,,,,
Well.. get my point. 
Since you asked, my idea of a workshop would be some instruction, and then a chance to shoot a few images, and they would not even have to be nude. Just let the guys see how much they can do on their own in a specific time slot. Ever consider that?
To be honest, $400 seems like a lot of money to sit and look at naked girls and take note.
Everyone have a great weekend, maybe I will have something new next week.