Bad news for you, there are no caravan sites on Jersey and you are not allowed caravans on the island. Here's a quote from relevant site
CARAVANS/MOTOR HOMES/CAMPER VANS/TRAILER TENTS There are no caravan sites in the island and caravans may not be imported. These are not normally permitted entry for any form of holiday use. In exceptional circumstances the Planning and Building Services Department Tel: 725511, will give permission if it is essential for the transportation of a disabled person with wheelchair but still not at any time for sleeping purposes. Only trailer tents which have canvas sides and roof are permitted. Those which, when erected, have rigid sides or roof and resemble a caravan are not