If I had 12 BTC I would hold 50% of Bitcoins and to invest the rest of Bitcoins in various coins. Holding Bitcoins will certainly be very profitable in the longterm run. I give Bitcoins a chance to grow in value by investing. I think I would invest Bitcoins in various promising altcoins.
I think you what you intend do with 12 BTC is very interesting because by investing in bitcoin you might reap great profits in future. However by involving in altcoins it will help spread your investment portfolio to investment class.