For our 25th wedding anniversary, we were very lucky to be given the chance to take the trip of a lifetime--a gift from my grandfather. As my wife has always wanted to see Santorini, and Seabourn's Odyssey was going to be there on our anniversary (with a late departure so that we could see the sunset in Oia) it seemed like the perfect opportunity.
I would highly recommend working with a travel agent in planning a trip like this, particularly if you don't normally do this kind of travel.
We had never cruised before--never wanted to, given the crowds and jostling that come with the mega-ships. We figured Seabourn would be the right kind of cruise for us, and they certainly delivered. In our mid-40s, we were not the youngest people on the cruise, though the majority were older.