I think @Paul_B has some bias against the on board regulator. Unless I missed, I didn't see the spec sheets I read required external heat sink for the specifications to hold, rather they quote ambient temperature. From my experience, you can go ahead with a single 9V supply. The supply will provide 5V through arduino's 5V regulator and will also likely be directly sent to your MOVI shield via vin as it requires that much voltage. Do mind how you enclose your project and whether it has some way of passive cooling, enough size for heat to dissipate, and away from direct sun light and heat source.