Powering Arduino pro mini and perihperals with 1S 2P 18650 batteries

I want to use 14 capacitive touch sensors (ttp223) to receive data from the user, then use 14 leds and 2 mini servos according to the given data. I wont give the complete description of the project since it is too long and irrelevant my problem. I want to power an Arduino pro mini 5v or 3.3v (the most suitable one according to the answers) with 1S 2P 18650 batteries. The touch sensors work between 2-5 volts supply, and give whatever voltage it is working on as output. I am not sure about the servos, I couldnt find any information on their data sheets. Servos are 90g mini towers. My question is since the battery will get depleted until 2.5 volts, would this affect the servos, the Arduino and the logic levels of Arduino? Should I use 3.3 which tolerates better lower supply voltages?

Servos need 4.8V to 6V, they won't work at 2.5V.
http://www.ee.ic.ac.uk/pcheung/teaching/DE1_EE/stores/sg90_datasheet.pdf
Letting batteries get down to 2.5V will likely damage them also, depending on battery chemistry. Many Li batteries for example have circuits built in that prevent discharge when 3V is reached.

I would suggest using a boost converter and running everything from 5V.

There are 14 leds, 2 servos, 14 sensors, a relay card and an Arduino. There might be around 5A current desen from battery. Total current would be a problem, thats why I dont want to use a boost converter.

Servos will be the big current draw; LEDs, maybe 200mA, relay card doesn't need much to energize the relay, Arduino maybe 100mA.
I haven't noticed 3.3V relay modules, most need 5v or 12V for the coil.
Servo's will need 4.8V to 6V, so 3.3V is a no go.
This regulator can boost 3.7V LiPo to 5V and up to 3A.