I'm coming to this post rather late but will share my experience. I took care of my mother for several years before she died. To be prepared for emergencies (and there were many) I always carried a flash drive with TrueCrypt-protected copies of her advance directive, power of attorney, POA for healthcare, photo ID, Medicare card, etc. A couple of weeks before my mother died I had to prove that I had the authority to determine who could be at her bedside in the ER, and my drive did the trick. Institutions will of course be reluctant to pop flash drives into their computers, but if the issue is whether you have the authority to make life or death decisions someone will find a way to view the files.
On the same drive I keep encrypted copies of my driver's license, insurance cards, home insurance policy, etc. If I lose my wallet 500 miles from home or my house burns down I'm reasonably well protected. You decide what level of protection you need.
The original post was about a somewhat different purpose but the principle is the same. Flash drives are more reliable and obsolescence-proof than CDs, but they can break. Buy sturdy ones, back them up, and test them periodically.