I email you weather course additional information letter your way to get an idea.
I am planning to go on Friday 26th with few other people to have an extra day at Newcastle.
Walk on at 8:45am ferry from Horseshoe Bay. I can help if you can come on Friday.
If not, I can link up with the other group taking Saturday 27th 8:45am ferry.
Either you can park car at Horseshoe Bay ferry terminal or Brechin boat launch 5 minutes away from Departure Bay ferry terminal. Their parking are inexpensive.
It is only 30 minutes paddle form Brechin boat launch to Newcastle Island camp site. Very nice Island, there are lots of paddling options or go for nice trail walks.