RC Toy Car Battery Upgrade and More

I am new to the world of electronics...
The other day, I planned to upgrade the lighting in my RC car.
My RC car runs on 4 x 1.2 V 2800 mAh rechargeable cells. The circuit includes 2 motors (Motor 1 for moving the car and Motor 2 for changing the direction). It also has 2 front lights, which glow when the car is in motion.
Here's what I want to do,
I want to replace the headlights with bright white LEDs and add 2 extra Red LEDs in the rear. I'll solder the LEDs on the PCB using wires in series.
While I was researching on the same, I found out that the LEDs might require me to upgrade my power source. As per Wikipedia (http://en.wikipedia.org/wiki/LED#Colors_and_materials), white LEDs need a voltage of 3.5 volts. So probably, when the car is in motion, the following will be in constant use
Forward: Motor 1 + 2 Front LEDs (3V + 7V i.e. 3.5V x 2) Nominal Load
Reverse: Motor 1 + Rear LEDs (3V + 4V i.e. 2V x 2) Nominal Load
Turning while moving Forward or reverse: Motor 1 + 2 Front or Rear LEDs + Motor 2 (3V + 7V/4V + 3V) Full Load
So, here's another thing, I don't want the LEDs to dim when the car is in motion or the car to slow down when it is turning. Neither I want the the car to go faster when it is moving i one direction (i.e due to less load on batteries). I mean I don't want the motors to be get extra voltage when the car is in under nominal load condition neither I want it to slow down or the lights to dim, when it's under full load condition.
Do I need to upgrade my power source i.e from 4.8V?
If yes, then can I use 2 9v Rechargeable 175 mAh batteries?
Also, as per the link below, to connect the LEDs in series, I would need to add a resistor to the LEDs, which will take another 2V
http://www.kpsec.freeuk.com/components/led.htm#series]Connecting LEDs in Series
Is that correct?
Also, lemme know if I would need to upload pics of my PCB.

lemonie7 years ago
I think that you'll have plenty of power in the car, as the drive motor will use most energy. Still a new power supply might be a general benefit all-round? You might want to use some kind of transistor-switching on this though. L