We use CampSpot for property reservations.
When searching for a property, choose your dates and select only 2 adults for the guest information. Do not enter girl numbers. You will see all available properties on that date(s).
Read through the descriptions and find the locations that will accommodate your group.
For day only reservations, please select the date you want to use the facility as the first date and then select the day after as the second date. The system is defaulted to overnight reservations but the descriptions will guide you to the day only sites.