After installing Intel's Bluetooth Driver version 17.1.1529.1620 for W10, I managed to connect Microsoft Designer Keyboard but *not* the mouse.
However, my other mouse a Microsoft Arc Touch Mouse was able to connect using Bluetooth.
And strangely, my Microsoft Designer Mouse connects perfectly well with my Surface Pro 2.
I do not know if it is a problem in the mouse or keyboard/mouse combo or Intel's driver....
Someone that knows how to make both keyboard and mouse connect to a Windows 10 system on a Intel NUC?