This sentence can be semantically correct by saying : They do not know YET about my wife and you. They "YET" can be placed before the phrase. They sentence can be correct "They do not know yet.....about you and my wife"
"They do not know yet about you and my wife" is an accepted translation.
but why not "mé ženě"?
both are possible and equivalent
In sentences like this after o comes an object in locative, right?
The recording of "o" in this program is difficult to hear at normal speed, it's pitched lower than the other sounds and goes by too quickly.
It sounds quite fine to me.