For a mechanical engineer you seem to have a pretty good idea of electronics, much better I'm sure than my understanding of mechanics.
The body diodes of the FETs (they are a side effect of the manufacturing process) would not snub positive going voltages. With the fast rise times of FETs you can get very high spike voltages on the drain, which tend to cause catastrophic failure. The snubber has usually a very fast diode a capacitor and a discharge resistor.
You should save some money and choose lower voltage devices as ronv suggested say 100v.
Since you also have 2 motors, instead of parralleling you could have 1 FET per motor.
Anyway best of success.