Reading current with YDHC SCT013 split core transformer and RPi or Arduino
Sampling 50Hz AC and averaging using math is definitely possible, an  RPi or Arduino will sample at 100Hz, no problem (and much higher). You could also rectify and smooth in the analogue domain. In that case you will still have some ripple, and will need to do some averaging also. But because you already rectified, you only need to do a running average, rather than an RMS calculation. If this is a one-off project, I'd personally try both (make a board with the analogue circuit, but be able to bypass it) and see which I liked more. It may be that eventually there isn't much in it.