I'm not the best of people to answer all your questions because it was a long time ago for me and I seem to have selective memories of it all. My mom reminds me of a lot of things that I went through. She said that the first day of my ATG was a little rough for me with chills and fever and such. After that, I seemed to tolerate the ATG ok. I don't remember if I was released the day after day 5 of my ATG or not. Sorry, I can't help you there. My mom said that the first few days when we got to the apartment we rented, I was sick with headaches and nausia. I do remember having a hard time taking the cyclosporine because it smelled so bad it usually made me throw up before I could even get it in my mouth. I spent a lot of time in the bedroom in the dark sleeping because of headaches. I remember just a general feeling of yuck for quite a while. It wasn't bad enough to have me down for the count. Just a general weird yucky feeling. When we tried to take me off the steroid, I had intense pain in my knees. The pain was so bad, I got taken to the ER a few times for pain shots. I remember that VERY well. I would say that immediately after his ATG, he won't be playing with is friends like a regular teenager. I can't give you a timeline of when exactly he'll feel well enough to do that either. Sorry. I was all so long ago for me. I know there are others on here who can help you a little more and I'm sure you'll hear from them soon.
Everyone is definitely different in their experiences. From what I understand, the younger the patient, the better they tolerate the drugs, though, if that makes you feel any better.
I hope it goes smoothly and he's the typical teenage boy you would expect to see soon.