Good question! There is not yet a tool that lets Hipcampers specify that there will be more or fewer people joining on one night of their trip vs another night.
Our recommendation is to have the Hipcamper select the group size that reflects the maximum number of people who will be in the group at one time and then make a plan with you as their Host to get the correct refund for the days where they had fewer people in their group. You have the ability to refund this amount from your calendar anytime after the camper books.