I would skip having any DNA sample in your BOB, as it could be lost along with the rest of your body and or ID. DNA also degrades over time. A better solution would be to contact a lab that specializes in DNA testing and deposit a sample in their repository and leave details and permission to access the information/sample with a number of individuals, such as family, close friends and your lawyer/trustee. That way if body parts were recovered it would make it easier to identify the remains from a known and well-preserved sample.

Pete