RozieD .... you're in my prayers! Your son is, too ....
In my family, we rarely exchange gifts for birthday and Christmas. My siblings and I draw names to buy ONE gift for each of the nieces & nephews for Christmas -- nothing for birthdays, and nothing for us grown-ups. STUFF just isn't that fulfilling, you know?
The occasional gifts that have been really wonderful and memorable were personal. When my brother turned 40, we assembled an album with pictures and cards and letters. We called old friends from earlier times in his life, and had them send cards, too. He was overwhelmed, cried, and just really felt the love.
Your son can get his own STUFF, more so or less depending on how responsibly he chooses to live his life. Send him something for his INTERIOR. How about making him something to hang on his cell wall? The AA Promises or some other hopeful text, like the Footprints poem or the Desiderata or something. Then around it paste pictures of things and people he loves or has loved in his past, like the beach, or a hobby or sport he once loved, or family members who are just aching for him to get his life together. Or even just simply the framed text, or another book but this time, write out a dedication on the inside cover with your prayers for his recovery and happy life.
JMHO. I'd nix the shoes.