I don’t know about the safety of the son. Really have no idea; other than to protect the reputation of the father. One point, though, is that megalomaniacs, especially ones who want to wreak vengance on others (he wanted Mau Mau to happen in the US), think everyone else is just as hateful and vengeful as they are. So perhaps (just speculating) he thought “they” would want to kill his son, since obviously “they” were after him.
Hard to read the mind of criminally insane people, especially without the right training in that field.