You could try the Tanunda Caravan Park
http://www.discoveryholidayparks.com...barossa_valley Plenty to do around there, especially if you take the bikes (I think you can hire), only a short drive to Menglers Hill lookout.
For slightly darker skies, I would think the Clare Caravan Park at Auburn
http://www.discoveryholidayparks.com...e_valley/clare would be pretty good.