I'd take a motorcycle trip around the world.
I once attended a seminar by a man named Jim Rogers, who had made his fortune on Wall Street, then took his girl friend and a pair of BMW's on a round the world trip. He had a lot of trouble in Africa, so I'd avoid that area, but the stories he told were fascinating. He tended to look at everything with an eye for investment potential, which doesn't interest me at all, but otherwise it was an interesting couple hours. I think he wrote a book about it as well.
So that's what I'd do. Start in Ireland, ferry to Britain, chunnel to France, hit my wife's relations up in Germany, then Poland and the Baltic States. I'd love to visit Stalingrad, just to walk one of the great battlefields of the world, but that might be a bit out of the way. Then across Siberia (in summer), down into China, catch a boat to New Zealand, then Australia. Cruise to Argentina, and drive back up to the States.