OPAMP-RC is I good idea at such a low frequency. You probably need to decide/get the order/filter type you require. At such a low frequency, capacitor area may be the greatest challenge. In an RC filter this can be directly traded off against resistance, and therefore noise. When looking at area, it is also important to think about calibration. Are resistors or capacitors or both going to be used to tune the filter? Is tuning actually required?
Just a few thoughts...