Good morning, WWD,
I'm glad that you will be able to see your son clean and sober, even if it may only be because he is in prison. I understand completely the desire to think hopeful thoughts about the future when our addicted children are sober.
We never visited my stepson during any of his prison or jail stints. He requested that we not, and we respected that request.
Enjoy the time with your son! I think just keeping your mind in the 'here and now' is a great plan.
Good luck!