Think of the companies that were once dominant or large players in their fields, but eventually faltered like Kodak, Xerox, IBM, TWA, Eastern Airlines, Author Andersen, Enron, MCI Worldcom, Montgomery Ward, Sears, Countrywide, IndyMac Bank, Pacific Gas & Electric, Chrysler, Lehman Brothers, Blockbuster, MGM, Borders, Harry & David's, Schwinn Bicycle Company, Reader's Digest, and the list goes on. What's hot one moment, eventually won't be. The ability to pick a long term winner is what the mutual fund managers are paid to do, but often can't.
This is the perfect opportunity to teach them how to build a diversified portfolio, instead of hoping for the home run.
So, I would diversify by following Buffett' and Bogle's recommendations for low cost index ETFs.