Something like this... Or a 2A on each of the cameras, instead.
That's correct. Note that diodes are polarity sensitive - although nothing breaks if you put them in backwards here - it just won't work. For most diodes, there is a band printed around one end of the diode that shows the end to connect to the cameras.
If you try to measure voltage without the cameras connected you will not see any voltage drop - current needs to flow for that to happen. So turn the voltage adjust on the power supply to the lowest output voltage, install the diode(s), connect the cameras, power everything up, and check the voltage after the diode.
Also, you need plain old Si (silicon) diodes - not schottky diodes. See what you can find from your electronics supplier and post a part number for me to check?
In any case, I may temporarily leave this out. There's 0,5V excess, as long as the power source can keep up with it, the cameras should be fine right?
It will probably work fine - there is usually a "safety margin" built into most electronic designs.
That being said, those little cameras were not designed to run continuously - most people turn them on, take a couple of photos, and turn them off. You, on the other hand, could be running them continuously for hours so there is going to be a lot more heat build-up than they were designed for. Made even worse by running them with too high a voltage on the input terminals (= more heat).
It's your decision of course.
