We're probably changing dates to not conflict with Easter.
Understanding the limits of everyone's availability, why not just make it when you make it and see what happens? If Easter weekend is good for you, then why not Easter weekend? If you lose two, you will also gain two. Here's the way it seems to me, if a person is really serious about going to this, they will be there. If a person wants to "fat mouth" and tell you the dates they can't go, but would really like to attend your class...which one is it? It's about opportunity cost simply. Will you give up X to attend this course? If not, maybe you should reconsider. Just let them decide a date and stick with it.