Good time of the year to be going to the Mackay region. There are heaps of good spots from Sarina to the Whitsundays.
I agree with CQCapricorn though Eungella is the best area. Eungella Dam is the best spot I have found so far. you can check it out at [url]http://www.campingqueensland.site90.net.au[/url] (The site is still underconstruction but you still might find it usefull)
Seaforth also has a good camp site on the beach may pay to book ahead though especially if your looking at the easter long weekend.