It can be a great vacation with the right people
4 years ago I did the BVI bareboat charter with two couples and four kids. My kids were 8 and 10 at the time. While they enjoy sailing, they are not avid sailors, yet they still consider it their favorite vacation of all time (even better than Disney World and much more fun than the one cruise we did take). We are planning on doing it again this winter.
I agree showing pictures is a great place to start. Maybe you can even find some where they show the cattle (passengers) lining up to go on excursions off the the cruise ship.
Be warned, however, that many consider such an excursion as camping on water. So, if you are dealing with high maintenance individuals you could hear some griping. Also, make sure you really get along with the people your going with because you'll be together just about the time.
Finally, unless the adults really dislike cooking while on vacation, I would pass on the cook as well. Some days you'll find restaurants to eat at, and other times you'll just want to take sandwiches onto an isolated beach.