I wouldn't mention it to him now. It's an emotional time for him. But I wouldn't get rid of it either. I would wait for a while (might be 3 months, might be a year) when he's not so close to the painful time and able to put the disappointment in perspective. Right now, it's the end of a dream but the pain will fade as it always does. That's the time to ask him if it's something he would want you to finish for him or if it would just remind him of an dream that wasn't achieved.