(As an aside, we did test with a Raspberry Pi, but it was just too slow. We've got 4 dynamic elements on the screen plus time, date, logo, weather and unfortunately the Pi just kept getting stuck with 100% cpu)
However we need it to shutdown right away if staff press the power button, not prompt with the confirmation dialog. Thanks to maketecheasier we found the following terminal command to sort that:
gsettings set com.canonical.indicator.session suppress-logout-restart-shutdown true
Press the NUC power button and it will be down in under 5s !