You nailed it. It’s just what you said: Cook the vegetables first at the higher temp, then plunge the bags into an ice bath to stop the cooking. Set up the SV at the lower temp, cook the meats and then add the vegetables toward the end to re-heat.
Can’t say I noticed any difference in the taste/texture vegetables that I tried this method with.
I would skip the full on freezer step though.
Not aware of a longer, low temp option for the vegetables. At one time I messed around with trying trying it anyway, all I ended up with was undercooked vegetables.