Using step-up converter in metering instrument?
I will address the "Main concern" directly - should you be using a switching supply to power analog sensitive instruments?

No. 

It is low power i'm assuming, so find a 2-cell LiPo battery and go straight for a linear regulator (LDO) with ultra-low noise and filter capacitor support such as the MIC5323 which states in the datasheet very low (20 uV rms) ripple. 

If you have higher power and less sensitive components, go ahead and use a DC-DC switching converter for those areas of your circuit.

Of course, you could try to do some serious filtering and testing on perfecting the output and quality of your switching supply. 

It is far easier though to use a linear regulator supply specially for the ADC related circuitry, and keep the power and ground loops from the regulator dedicated only for this area, and connect the ground of the LDO to the system ground somewhere else, perhaps even decoupled with ferrite beads and whatnot.