I'd say if you're on a reccie, you probably don't want to stay in the City. Much too say in all directions. With the temperatures you would want to wear warm clothes and perhaps do a bit of a road trip in between outings.
If you do go down south towards Victor Harbor or Port Elliot for whale watching, and you want to see some Australian nature, you could also go to Urrimbirra Wildlife Park, or if you want to see the roos in the wild do one of the beautiful walks in Deep Creek NP, or drive to the coastline around Myponga or Rapid Bay.
For the wine tours, the Tourist Information Centre in McLaren Vale can give you a map of all the wineries, and tell you which ones have playgrounds for the kids.
And I agree with Howde that there are many beaches you could go to. Semaphore, Glenelg, Brighton, Hallett Cove, Port Noarlunga, Moana, Aldinga Beach, wherever you want to go. Bring a thermos or get some take away coffee on the way!