Does he have any important past emails that he needs or would he be able to do without them?
If he can do without them without negative effects upon his life, then just put a number 2 after his old screen name and create a new account.
This way it will be easy for friends to remember rather than switching to a totally different screen name.
Tto prevent this happening again, have him put his password and recovery info into a sealed envelope to give to you (or someone else whom he trusts) to be opened only if necessary.