Hi Michael,
Would not want to put a dampener on any proposed visit to Orkney, a wonderful place, but something to be aware of is the crossing to Orkney.
Carried out a lot of contracting work on the island over the years and the Pentland Firth can be quite a "lumpy" crossing, have witnessed vending machines coming adrift in the galley and several other incidents.
Providing all your party can travel by sea happily go for it but as I say be aware of the possibilities.
Sorry never witnessed "the lights"
Regards.