The caravans in this case are a type known as static caravans - basically the same sort of accommodation as a mobile, towed caravan, but usually bigger and more or less permanently positioned somewhere. They even sometimes have additional casings that hide the wheels underneath to make them look more like houses.

EDIT, as I didn't answer your main question. A caravan park is a term used both for something like a trailer park, where customers tow in their own caravan, but also, as in this case, for a holiday park with these static caravans spread around, similar to small lodges.

Behind the bar - yeah, that's what they mean here too, the people who serve at the bar. As it's in a holiday park, it's likely that it's a family friendly bar where kids are allowed to be as long as their parents are with them, and can even probably go up and order snacks or soft drinks by themselves. It's not a bar bar in the usual adults only sense.

Tragic story :-(