I've never heard of a trailer stolen, altho we had 2 pricey bikes and a canoe, all chained up, stolen in a gated campground. If someone wants your stuff badly enough, they will get it. But trailers in campgrounds just don't seem to disappear. Hitchlocks, sharp-eyed neighbors, watchful campground owners, all combine to make it very unlikely. Plus, people are going to take a special interest in looking after a "single mom" and her kids on the road. A stranger wandering around her site or messing with her trailer will attract attention.
Personally, I prefer the truck and trailer option, too. But it is trickier to drive than a class C by itself. Make sure you get some practice.