Ohana Isle Treasure Hunt : The organisers don't want hints and i respect there wishes. It is simwide and can be found here . This one is once a month; HUD based. You get the HUD from the vendor (L$0) at the starting point, wear it and it shows you which treasures you still need to find. If you find all treasures, you can get an extra prize from a vendor at the starting point.
Treasure Quest Hunt (TQ) : There are usually 2 a month at this location so check it out.
mid-month TQ - 14th-20th (this time: 21 stops, 7 of them have a B clue, too)
end of month TQ - 28th - 3rd September
TY TO NODDY, the little woman in the red and yellow car, for this information. He is my little star.