Kangaroo Island is Australia's third-largest island, about 145 km long with 540 km of rugged, cave-riddled coast, and a ferry ride from Cape Jervis. The 2019-20 bushfires burned nearly half of it, including about 96 per cent of Flinders Chase National Park; the park has since regrown and reopened, and the island's sea lions, penguins and wild coast are all still there to see.
The camping spreads from one end of the island to the other. At the eastern end, Kangaroo Island Seafront Holiday Park is in Penneshaw by the ferry, and American River's campground sits beside Pelican Lagoon. On the south coast, Vivonne Bay Campground is near the beach and jetty, and at the western end, the national park camp at Rocky River puts you close to Flinders Chase.
On the south coast, Seal Bay Conservation Park protects an Australian sea lion colony of about 800 animals, with a boardwalk as well as guided beach walks. Kingscote has a colony of little penguins, the smallest penguins in the world, and at American River, Pelican Lagoon, named by Matthew Flinders in 1802 after its pelicans, is good for birdwatching and kayaking. Hanson Bay Wildlife Sanctuary is near the western parks, and in Penneshaw, the maritime and folk museum is a short walk from the ferry. Up at Cape Borda, the lighthouse dates from 1858 and is the only square stone lighthouse in South Australia.
In Flinders Chase, the Admirals Arch boardwalk and Remarkable Rocks are open again after the fires. Kelly Hill Caves are one of the island's cave systems; it had 120 caves catalogued before the fires and about 150 more found since. Billygoat Falls and the lookouts around the Ravine des Casoars, named after the extinct dwarf emus once seen there, are further out on the west coast.
Yes. National park campgrounds on the island are booked through National Parks and Wildlife Service South Australia, and the ferry should be booked ahead, especially with a caravan or trailer.
None of the campgrounds here have powered sites confirmed yet. That usually means nobody has confirmed it, not that there are none, so check with the park or holiday park before you book.
Kangaroo Island is about 112 km south-west of Adelaide, and just 13.5 km across the water from the Fleurieu Peninsula at its closest point. Penneshaw, the ferry port, is about 107 km from Adelaide, with regular ferries from Cape Jervis.
Facts from Wikipedia, "Kangaroo Island" (CC BY-SA 4.0), Wikipedia, "2019-20 Kangaroo Island bushfires" (CC BY-SA 4.0), Wikipedia, "Seal Bay Conservation Park" (CC BY-SA 4.0), Wikipedia, "Cape Borda Lighthouse" (CC BY-SA 4.0), Wikipedia, "American River, South Australia" (CC BY-SA 4.0), Wikipedia, "Penneshaw, South Australia" (CC BY-SA 4.0) and National Parks and Wildlife Service SA, "Flinders Chase National Park".

Region boundary: ABS ASGS Edition 3 Tourism Regions 2021 (Tourism Research Australia), CC BY 4.0.