@Hamish39 You create a separate listing, under the same account, for each caravan. You only show that particular caravan in the photos, along with photos of the outside and any common areas guests share, for instance, a firepit or outdoor eating area.
Then, you should mention in your listing description, that the property has XX number of caravans for rent, and that if a group would like to rent more than one, to click on your profile page to see the others.
All of your listings will show thumbnails on your profile page, and guests can click on any of them to see the full listing pages.
It's important to get across, in your listing wording, that there are other dwellings on the same property, with other guests, lest they arrive with the misconception that they have the entire property to themselves.
But with that much land, I imagine you will spread out the caravans so that everyone feels private.