Happy Birthday to your little boy. Five years ago today, you brought that precious baby into this world. Huge day for both of you!! Congratulations!!
I don't believe in coincidences. I find something strange about him texting you on your son's birthday without acknowledging him.
Also, if you contact him....you are showing him you (and his addiction) that you are not a person of your word. He has set the bait, it's up to you to take it or not.
I pray you stay true to yourself and all your blessings. I pray you embrace today and not a "hopeful fantasy."