Does H know he can look at the website to find out the information? Would he have known this irregardless of the sitch ?

I think if it were me- I would send a brief text about the conference time and date and give H the opportunity to mKe the decision on his own. I just think that when it comes to things like this it's ok to give the information and leave them to decide what they want to do.

TPS
Me: 44 H: 42
M14 T17
S10 D7
10/10 H moves out after death of his father-same month
21/04/12 H is 'DONE'
04/05/12 OW/PA confirmed (rumors from 2010)
July '14 H ends affair
May '15 H moves back home