The arduino mini pro can have this voltage. In fact it is the same processor as on the 5V versions, only the CPU runs on a lower frequency.
The most simple solution to power the NRF is with a LDO regulator for example lp2950-33lpe3
I’m not sure if it is possible to power the arduino on a higher voltage then the NRF because they are connected via IO. So probably it is better to have them both on the regulator.
If you want to save battery program the arduino on 1Mhz (see above), removeLEDs and sleep very often