This is the end of the Murray, where the river runs into Lake Alexandrina and the Coorong, a lagoon about 130 km long behind the dunes of the Younghusband Peninsula. It is Ngarrindjeri country, the ocean beach on the far side of the dunes runs 194 km, and Jack Point holds the largest Australian pelican rookery in the country.
The camping follows the water. On the river, Murray Bridge has the Marina Camping and Caravan Park, and at Tailem Bend, Waterfront Holiday Park has powered sites and showers. For the Coorong, Meningie is the gateway, and Lake Albert Caravan Park is on Lake Albert, used for swimming, kayaking and fishing. Inside Coorong National Park, the park service describes 42 Mile Crossing as its most family-suited campground, with space for tents, camper trailers and caravans.
Around Murray Bridge, Sturt Reserve on the riverfront has a playground and the Bunyip, a mechanical water monster in the riverbank, and Monarto Safari Park is about a quarter of an hour's drive. Near Tailem Bend, Old Tailem Town is a pioneer village of more than 110 old buildings, and the free ferries at Tailem Bend and across the Albert Narrows are an outing in themselves. In Meningie, the Cheese Factory Museum is a short walk from the park, and out on the highway, Coonalpyn is known for its painted silos.
In the Coorong, the Lakes Nature Trail and the walk to the Jack Point Pelican Observatory are the family-sized walks, and the wetlands around Meningie draw birdwatchers for their rare and vulnerable wildlife. Upriver, Younghusband looks over Lake Carlet from the cliffs, and out east, Ngarkat Conservation Park near Lameroo is known for spring wildflowers.
For the Coorong, yes. Coorong National Park campsites have to be booked ahead through National Parks and Wildlife Service South Australia, up to 12 months in advance.
Yes. 2 campgrounds here have powered sites confirmed: Waterfront Holiday Park and Lake Albert Caravan Parkl. For the rest we are still confirming, so check with the park or holiday park before you book a powered site.
Coorong National Park is about 156 km south-east of Adelaide, with road access from Meningie, 108 km from the city. Murray Bridge is about 78 km and Tailem Bend 85 km south-east of Adelaide.
Facts from Wikipedia, "The Coorong" (CC BY-SA 4.0), Wikipedia, "Murray Bridge, South Australia" (CC BY-SA 4.0), Wikipedia, "Tailem Bend" (CC BY-SA 4.0), Wikipedia, "Meningie, South Australia" (CC BY-SA 4.0) and National Parks and Wildlife Service SA, "Coorong National Park".

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