Yes, you do need smoothing capacitors, see the ADUM6401 datasheet for the recommendations. I attach a schematic of the arrangement I have used when I need a 3.3V output. For 5V output you need to connect pin 10 to VDD2 instead of GND2, also increase the LED series resistor. The LED provides the recommended minimum load of 10mA. C6 is the decoupling capacitor for the MCP3204 and MAX6145.
EDIT: also you need to connect pin 12 (AGND) of the MCP3204 to the isolated supply ground side.
