Larry,does the vibration change when changing from drive to reverse? When pushing "EC" and then the middle ACC button again? Have you tried slightly unloading the engine mounts and rear trans mount while the engine is running w/ the daughter inside to listen for changes in pitch or tone. Does the car have the "capture mount" right behind the oil pan? If so . slip the retainer clip off of the 19mm bolt head and loosen the bolt about three turns then retighten it.Also, the rear mount has a 6mm tool size allen facing aft. Do the same this bolt, then grasp the drive shaft and pull down.You should perceive 3-5mm deflection. If not, replace the mount.
If this is more of a felt vibration than audible, a torque converter rotor bearing failure may be the deal, and will have sluffed off swarf throughout the transmission. u know what that means.
Check the easy stuff 1st ( u know that too)