I'm not sure he has the "right" intention behind wanting to donate.
I don't know, it seems weird to do it so that one day you may get to meet "your" children. I believe if you donate you really need to look at it as if you were donating blood etc.
Given what you told us I would ask him not to go ahead with this. Or at a minimum have extra counseling session where you open up and explain your reservations.