Do not acknowledge the day to him. Leave it alone. If you want to acknowledge it yourself, have an ice cream cone or something, but don't send a text message, email or call him up.
Your son will be spending some time w/him and that's all that matters right now.
Focus on you 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.
