Organise your own tour on Orkney (through tourist board site) and include Scarabrae, ring of Brodcar, stones of stenness and Maes How which has loads of REAL viking 'graffiti' which are all in the same area, and then go to the south isles over the 'Churchill Barriers' (stop at the italian chapel)and see the most beautiful scenery and beaches that rival any in the caribbean. Alternativly see if you can get to Rousay an island close to the mainland, which has many Viking sites. Dont miss the cathedral in Kirkwall either. As you may guess I love Orkney.
In Orkney suggest you visit the "Ring of Brodgar" which is a historic site older than Stonehenge. Also the ancient site at ScaraBrae is well worth seeing.