To buy a round the world ticket and travel to as many places as possible (with my family, of course, but maybe with a full-time babysitter to help!) Top of my list: India, Nepal, Bhutan, Laos, South Africa, Chile, and Mexico. Well, that's for the first few months anyway!
My choice would be to become a 19 years old again and go to University, have one more degree in business and run a successful business here in Canada. I know it is not possible, if it would be, I would be very happy to buy a round the world ticket and travel to many countries like LauraGT said.