The Dunyain don't seem to but much merit into plan "B" (no pun intended). Moe thought he'd survive the encounter with his son. So why spend the time and resources rearing children properly? After all, left to their own devices the Dunyain children go mad.
Moenghus had his hands full rasing a sing child in secret while attempting to control the Fanim and rouse the Inrithi into a Crusade. I don't think he had the resources to raise a brood of properly functioning children.
Its kind of a "pick one" secnario. Either dominate the world or raise a brood of world-dominating children. If you pick world domination, you can either have 1 (or maybe 2) successful child(ren), or a brood of autistic savants.
It would seem that raising your own army of super-children would be the way to go, but I think it goes against the grain of Dunyain rationality. Once in the world, domination is everything, and even a full blooded Sayin, errm I mean Dunyain, would lose control given enough time and enough children. The parent would eventually be dominated by the children, and this is unacceptable.
It works OK in Ishual everyone is working towards the goal of dominating TDTCB, rather than eachother. Inevitably the children surpass the parents, but that is the whole point, its how they eventually hope to create a Self Moving soul. But once they are not all bent towards the same goal, they would fight amonst themselves to be the best Dunyain currently alive (Highlander).