I reckon if you can get the car and yak to the Platypus Bay side of Fraser, and camp at Wathumba Creek or Awinya Creek you would be set. A prowler would be ideal. I would perhaps reconsider the idea of a PA sail and save pennies for a Shark Shield, but ask anybody and they'll tell you I'm paranoid. I can't speak for Wathumba Creek as much as Awinya (I've fallen in love with the place), but the LongTail tuna are usually busting up from 200 meters to 2 km off the beach when they are on (its late in the season now, so it would be more rare to see that at the moment) but the distance is obtainable in a prowler. As you can see in the vid, the beach launch is a dawdle so you don't need to concern yourself about that, have a look at the pictures of the beach here and you'll see what I mean:viewtopic.php?f=17&t=52420
If you're after Goldens, have a look at this: viewtopic.php?f=17&t=46645
Roo1 picked up that Golden T just 30 meters off the beach.
As for Mackerel, they come and go, last trip they were in plague proportions but pretty small in size, the trip before that was the mackerel season but we only scored 1 between the 3 of us. Regardless to say, if you can get the prowler to water in Platypus Bay, I think you'll get your goals and eat well.
Red is always good for advise and safety tips but he's claiming a "miserable" time on Humpy Island this week, you could hassle him for info next week and get another perspective.
If you do plan a trip up to Platypus Bay, post a trip plan, who knows, maybe some people could meet you up there, either taking a car, or sailing/peddling or paddling over. I think somebody else was talking about a car trip over with kayaks on the roof, maybe you could coordinate with them, there's always people keen and a lot of yakkers would jump at the opportunity to go. I will certainly be planning another trip next year.