I would start to advertise next Jan/Feb for Sept 2014 spaces as that is when parents register for JK. What if you advertised and filled a space and then a parent turned around next Jan and said we have decided to hold our child back a year so he won't be going to school this year after all?

Also I agree, the baby needs to be born and the parents have an idea of what kind of environment would best suit the baby - do they love excitement, need quiet, etc.