Clark Jungle Hammock makes a two-person hammock called the Vertex.

You shouldn't have a problem leaving a hammock set up at a campground, but they are also easy to put up/take-down if you feel you'd rather keep it with you.

For high elevations, you'll need to be prepared for the swings in temperature and precipitation, so having good insulation (down quilts, top and bottom) and rain protection will be key.

Most hammock set-ups are less bulky and lighter than other options. A simple gathered-end hammock, for example, packs to the size of a large grapefruit and can be stored almost anywhere. Sleeping bags and pads are the biggest and bulkiest parts of any camping kit, usually.