Treese, I'm glad to see that your son is back home safe and sound.
So, he's going out of town. Don't contact him, let him go. Pretend he's on a trip abroad and his cell phone isn't working. If he calls you, wish him a pleasant trip, otherwise, stay quiet and still.
About the birthday, purchase something for the children to give him. If you really need to purchase something for him, something maybe like a gadget or something impersonal for now. No gushy type cards, very few ILU's. The ILU's, phone calls, etc. are pressure points w/him. Give him a wide berth and just leave him alone.
You are starting to sound anxious again. We all go through this and btw, what you are experiencing are really withdrawal pangs from the "fix" that you get from your h. I know that sounds crazy, but we all go through it and once the addiction is under control, we detach even further and do not react quite so much to what they say and do. Find things to keep your focus elsewhere. Have you look at your tattoo today?
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.