it's obviously about kids... radiation therapy and chemo can in fact cause lower sperm count or actual infertility, which is why he didn't pull the trigger on all that. And surgery is pretty fucking dangerous in that area. There are workarounds for that obviously like freezing some sperm but let's just wait until we get the full story and his perspective on all this, because we don't know everything yet.
My theory regarding sperm freezing being a no is... that it could take much longer?
1. Fertility clinics can take much longer to schedule sesssions
2. while per cycle odds are higher for IVF compared to normal sex, the cumulative chance is higher for the latter (e.g 40% odds for one IVF session vs 20% for normal sex, but that 20% chance is highly frequent, whereas the 40% is limited)
Accounting for the limited time he has, the birth could happen after he dies which would probably create a lot of issues when it comes to inheritence which is the whole point.