Shetland Isles

As we are in Scotland at the moment, the Caravan Club Site in Garlieston, and tomorrow we move over to Lidalia at Newcastleton we are thinking of giving the Shetland Isles a try as we've never been before. I've just checked the ferry prices from Aberdeen and for our motorhome which is just under seven and a half metres long the ferry costs are around the five hundred pounds mark for the return journey. Has anyone been with a motorhome around our size and if so is it worth going? We don't cycle and so use the motorhome for side trips hither and yon. Also, I've looked at the Shetland Island Council site for information regarding the sites available and to me they don't look too inviting. Would I be wrong in making this assumption or am I being a little bit too cautious?

David.