Robot Commando

I am building a "restomod" out of my 1960-era Robot Commando.  Since I have very little little micro controller or coding experience, I'm hoping that members of this group can make some suggestions or recommendations.

General overview:

The Robot has two motors, the original 4.5vdc motor to operate the robot's functions and my added 12vdc motor to operate a linear actuator which controls when those functions are active.

The 12vdc motor is a Pololu 20D with a magnetic encoder attached to position the lead screw / linear actuator.

The robot has 7 functions; On, Off, Forward, Turn Left, Turn Right, Fire Missiles, Fire Rocket - each controlled based on the position of the lead screw / linear actuator.

The robot will be operated by offline voice commands.

Based on these specs, which controller do you recommend?  Does Raspberry Pi better lend itself to this project than an Arduino? If so, which model?

Since one motor draws approximately 120mA and the 2nd about 270mA, I will need to add some relays.  Your recommendations?

Suggestions for a voice controller?

I'm planning on using a dual output lithium battery pack to power everything.  Any experience you've had with these will also be useful.

I will be posting photos and videos of the project as he progresses.

Thanks for your help!

Casey