Hi Ongman - no-one's got back to you yet, so I'll give you my 2c worth - although my information's about 12 months old.
The sand track into Poverty Creek was pretty easy for me - I have a MWB Landcruiser, and I'm pretty sure was in 2H most of the time. The sand was nicely packed for the most part, with some soft bits in the corners.
We took the track up to the northern end of the island and it was a lot softer and harder going, but pretty good fun all the same.
There is no ramp at the camp ground at Poverty Creek, so unless you can lift your boat in, launch back at the ramps at Bongaree, Donnybrook or Toorbul and take the boat up by water.
Hope you have a good time - it's a nice spot. Take the bug spray
cheers,
Mark