Yep, we've been there a few times. Beautiful beach. I think it's even within walking (a long walk) distance of Kingfisher along the beach, and the tide's right, but best to check that claim through other sources.
The track to the jetty area is rarely cut back or graded, so when we did it the first time in the Jimny it was an easy run. The second time in the Triton, and we got a heap of bush pin striping and a few scrapes for our troubles. Still, a good spot.
A quick google got me this:
http://www.upstreampaddle.com/media/Mackenzie's%20Wharf,%20Fraser%20Island.pdfcoordinates are apparently here, according to that doc: 25° 24’ 25” S, 153° 00’ 46” E - mapped here from Google Maps