We stayed at Hole in the wall june of last year and very much enjoyed it, incredibly beautiful location. The best spots do not have any hookups. We stayed at site D which has the one the best views. I have a 20' Safari and while out site was a bit tight I was able to maneuver the 20 footer there easily. This is one of the reasons I love the 20 footer.
There is NO fee for crossing to Grand Manan Island. Fees are charged on the return sailing to the mainland.
The ferry cost me a little over $100, rates are $8.20CAN a meter.
I would definitely go again and spend longer next time around.
Here are a few pics.
I am sure you will enjoy it!