12V motors are controlled by which motor driver ?
other motor is controlled by which motor driver?
Any link to the motors? ( both of them)
What you could do is use a 12V source and use one switching regulator to bring it down to 5V and make sure the regulator can provide upwards of 5A ( being safe) . Also your battery is pretty hefty - which one are you using
Btw I know admin or someone else is going to scream at me for using regulated power for servos but the truth is that if your regulator can provide more amps than all the servos drawing at stall torque - then you're fine.
also , may I ask what you are building ?