Go with option #2, the designer monitor. My colorist friend has already purchased two of them, and I am soon going to do the same.
Over the last 5 years I have used both a 30" and 24" Dell Ultrasharp monitor and found that my 24" had terrible calibration compared to the 30" model (it was much warmer in color and didn't seem like it had the best color gamut in comparison). I couldn't fix it with a color calibrator either. Even if your son isn't doing much color work now, down the line it is likely as an editor you will learn at least basic color correction, so a 100% SRGB monitor is a good way to future-proof your workstation setup.
It's only $330 for the QHD version on Amazon. Not sure on Australian prices but should be just as good of a deal. Buy two with a VESA dual monitor mount for $35 and it will be a major upgrade. Also make sure to get a $10 10-foot display cable for one of the monitors as it is likely you will need the extra length with this kind of configuration.
I would also recommend looking into the Razer BlackWidow Chroma v2 keyboard and Logitech Master MX 2S mouse. They are a bit pricy, but you get what you pay for. Incredible ergonomics, programmable shortcut buttons, build quality, etc. I don't know how I would get through long editing sessions without them, now that I have them.