Seaforth area between Proserpine and Mackay. There are 4 camping areas around that area. We stayed at Seaforth years ago and all of my 4 kids loved it. The showers were $0.20 for 3 mins hot water and you camped where ever, there was no designated sites. No power sites though. I would reccomend those areas.
Seaforth camping reserve, Halidays Hidaway, Ball Bay camping reserve & Smalley beach. All nice spots. If you have Camps 3 or 4 books they are # 61, 62, 63, 64 on the map in the book.
Life is what happens when you've made other plans.