Hi Denis,
We went over to Orkney in 2005 (August), booked through Carefree (CCC).
We went Scrabster to Stromness on Northlink, very nice new ferry, past Old Man of Hoy.
We stayed at The Pickaquoy Centre in Kirkwall, which is a fairly basic site with hook-ups and hard-standing, about 5 mins walk from Town Centre. Our only 'problem' was that it was the Annual Sheep Dog show, which was being held at the Pick. Centre, and all the little 'darlings' with their pooches seemed too be staying within 50 yards of us! With some people having 5 or 6 dogs, it became an irritant with the continual barking or training on the site, irrespective of the other 'residents'.
Yes it was brought to the attention of the Site management, but realistically what could they do, with only one other site on the island?
All I am saying is that unless you are a doggy lover, do some homework and avoid this Dog Show if you value peace and quiet.
As for Orkney itself, what a lovely unspoilt place!
I would imagine onward travel to Shetland would not be a problem at all, as ferries leave from Kirkwall on a regular basis.
Not a problem at all going over to Orkney with a caravan.