In about 12 or 14 years of caravanning, we've only ever had one thing stolen.....our metal double steps, and that was from a large commercial site which had some undesirable types (by the warden's own admission) staying. By the very nature of it, caravanning means large amounts of stuff are left out in the open, or in awnings (and, let's face it, even a locked caravan isn't really that difficult to break into!). By and large though, it is very rare for anything to go walkabout - most caravanners/campers seem to be an honest lot and respect each other's property. There are one or two sites which have a bit of a reputation for things, quite often bikes, going missing - a trawl through forums will give you the details. These tend to be the larger sites with either no/inadequate perimeter fencing, and which the public (not staying on site) have access to. I don't know the site you're going to, so can't comment on it, sorry. Generally speaking though, I don't think you have any great need to worry.