HiRez to Redbook

May I recommend you NOT down-convert them? Just play the music 24/96 through your mac using Audirvana or any other music player of yr choice. The difference between 24/96-192 & 16/44.1 is not subtle.
If you must, then most media players will do it for you; if at all possible, try converting the sample rate first and then do the dithering. Good luck!

My new Honda Accord automatically down converts any file higher than MP3 to MP3, but it at least plays them without requiring me to convert the format

DbPoweramp will down convert a DSD file to whatever you want.  You won’t notice the difference if listening in a 🚗 .

FYI...I use dbPoweramp on my iMac.  Great program

Thanks guys. 
gregm I agree and do play them hirez on my HiFi rigs. To be more specific my intentions were to play the physical CD in a car. Don’t really want to explore hirez playback options in the car and don’t want to repurchase music I already own. This is why I want to down sample. Thx, Jeff