Thanks to the help from this forum, we had a fabulous trip to Kangaroo Island.
We decided to fly into Adelaide and take the ferry. The cost was less (since there were 5 people in our car) and we could see a bit of the McLaren Valley before the ferry ride. The Coriole winery as really great and the lunch is fabulous (advance reservation required). We found that Thrifty in Adelaide had no problems with a car going to Kangaroo Island (ditto for Hertz but they were more expensive).
The ferry is fun and easy, be sure to be there at least 30 minutes ahead and reserve in advance (of course we were there Christmas week),
We got our groceries at the IGA in Penneshaw, which was reasonably stocked. We did end up driving after dark but it was not a problem.
We rented a 4 bedroom house on the north shore near Snelling beach, called Tammar Ridge. The pictures on the website looked too good to be true, 35 acres of grounds overlooking the beach, a huge living area and deck. The entire living space featured floor to ceiling glass. However, it was better than the pictures. Really beautiful, comfortable and extremely well equipped in every way, from kitchen utensils and appliance to beach supplies.
Our first day was as trip to Seal Bay and a ranger lead tour. Wonderful! Great information, beautiful place, up close with the sea lions. We then had lunch at the Vivvone Bay General store, really tasty! The young chlidren and their grandparents went back for beach and naps while the rest of us did some sandboarding at Little Sahara, after a walk on Beautiful Vivvone beach. There is no need for a tour, just rent the board for $20 at the general store. The sand dunes are 5 minutes away and it is fun to try.
Back at the house (both in the morning and at dusk) there is LOTS of wildlife right off the deck or a short walk away: kangaroos, wallabies, and great birds(we saw an ealge, a darter, galah and lorikett). Great fun!
The next day we went to Flinders Chase National Park (at least some of us did). We did the snake lagoon hike, the Admiral's arch and the Remarkable rocks. Lunch at the visitors center was very tasty. If I had it to do over, I would skip Snake Lagoon hike and go to the Hanson Bay wildlife reserve instead, or get an earlier start (not my group).
Our third day was spent at Snelling beach, checking out of the house, then lunch and afternoon at Stokes Bay. Good food, interesting beach with cool rock tunnel and tide pool. Onto the 5:30 ferry and overnight at the Anchorage at Victor Harbor. Great dinner at the beach cafe, really good food at really reasonable prices.
Wish we had more time. Those of you lucky enough to live in Australia should take a week to do what we had to do in 4 days.