Assuming your only interest is in selling the fleet?
If you can get information on the boats (year, make/model, length, engine hours, photos) someone might be able to advise on a value... the remote location is obviously going to be a big factor.. probably your best bet would be to find a local who wants to get into that business. Not easy to do from afar..
Best of luck.
Option B.. take up sailing and do it yourself!