Myself and a friend have had unusual experiences - and have heard of others - when it comes to dealing with prisoners and bureaucracy as well.
For some unknown reason, spiritual books and some personal growth information just seems to get through the system. We decided that if it was meant to happen - it will!
I personally sent someone information on AYP and techniques to help drug addiction and it all went through, even though there are strict rules about printed paper, books etc not being accepted.
A few years ago a person went to prison with the book The Celestine Prophecy in his belongings. All his belongings were locked away until his release - except The Celestine Prophecy book.
It was read by nearly all the inmates, for months it was circulated and it can only be presumed that is was 'meant to be' and helped many people.
So, my suggestion would be to send whatever you can anyway and see what happens - leave it to the greater power that seems to have more 'power' than any human enforced system..
Amaargi