As the majority of the coastal area is covered by Parks or Reserves & bordered by private property the oppurtunity to free camp is a bit limited particually for groups. Camping on the beach it's self is not normally allowed but quite a few small formal camps are spread throughout the back beach. The caravan parks at Beechport or Southend are ideally situated for day runs through Cunundra & up to Robe.
We found great accomodation available in Robe & Beechport but could be booked out & very expensive at xmas.
Beach conditions change with some being very trecherous but there are always options to get around. A few Rangers get about at times so keep the drinking low key & you'll have no problems.
Fires are OK given the usual summer restrictions.
Download these free maps
http://www.westprint.com.au/freemaps/ from tha Wattle Ranges 4x4 club as a start.