2 x 2 n-channel mosfets in series: does my circuit has any flaws?
If you wish to use n-channel MOSFETs as static switching elements, you will need to create an auxiliary power supply rail. To drive a high side n-MOS into triode you need bring the gate 5 V to 10V above the supply rail you're switching.

Some gate-drivers include a bootstrap capacitor to operate as a charge pump. However this requires that the load is being switched periodically and not a static output.

So, you can either generate an auxiliary power supply rail above VCC with a charge pump or boost converter.

Or, Implement your design using p-channel MOSFETS. Just make sure not to over-drive the gate beyond its rated Vgs (a zener clamp works well here).

You will also want to include bulk and decoupling capacitors as well.