I think the proof is that this problem has only been an issue for several months. And yet you've been in, around, and driven cars all your life. Engines are exponentially more oil, vapor, fume, and odor tight now than they were 20, 30, 40 years ago. Unless your engine/transmission is excessively worn, neglected, or damaged, oil fumes/vapor/mist are simply not present in any significant amount in the normal operation of a car.
Now I'm not saying that a 20 year old car with 250,000 miles doesn't produce more tailpipe emissions and more "blow-by" than a new one, but the increased amounts are easily handled in a well-maintained drivetrain. One need only to look at a parking lot today vs. 20 years ago to see how much less oil leakage and seepage is a problem these days.
You say your wife and kids ride in the car with no issues. Other people can note no unusual odors or fumes. Several (am I correct?) shops have addressed the issue and found no faults. Auto mechanics and auto service people aren't suffering increases in lung cancer or respiratory issues lately, and you say you're experiencing similar issues in another car as well. I'm not sure that the problem is with the cars.