Hi,
if great accuracy is not required you may do anything... ;-)
REF-Driver: be sure it can handle 2uF directly connected to it´s output. Maybe a 100R (mabe less) from output to C could be helpful.
Be sure the REF source is stable and free of noise. An RC low pass in front of the buffer should be a good idea.
What´s the use of the OPAMP unity gain buffer at the signal input? It depends on signal source impedance, signal bandwidth, cable length if it´s a benefit.
If the signals are of low frequency .. an RC shouldn`t be too much effort.
******
From the accuracy and precision view:
* use the same REF for ADC and signal source - if possible
* use separate GND_sense wiring from signal source back to ADC AIN-. With identical source impedance than the signal line itself.
* Treat signal line and GND_sense most equally.
* Use at least a simple anti aliasing filters in front of the ADC.
Klaus