#2 L7809CV regulators, connected to #2 9vdc motors
If I am getting it correct you wish to run only one motor at a time.
That can be simply done using only one LM7809 and a SPDT switch.







simulate this circuit &ndash; Schematic created using CircuitLab

I guess that is too obvious. So would you like to add more info. Like any specific control mechanism( supposedly to replace the manual SPDT switching).