Switching regulator to power motor
Your input range is very close to the output voltage and then a buck/boost regulator is useful.  

  

This one has a 95 % efficiency and a 5 \$\mu\$A shutdown mode. You set the output voltage with the resistor divider R1/R2. Note: this comes in a small package, which may or not may be an advantage.  

Anyway, there are many buck/boost converters with an enable input. You'll find a list from Linear Technologies here.