I think the pension buyback is definitely a smart move even if it's a bit of a financial hit right now.
As for "sharing the wealth", I'm thinking maybe a lot of the hesitancy about sperm donation is concerns over privacy and anonymity? How would you (and your family) feel if 18-year-olds started appearing on your doorstep a couple of decades from now, saying they;d done some research and concluded (whether rightly or wrongly) that you were their dad?