This.
I think you’ve had a bit of a rough ride, OP. I recognise some of the most thoughtful and moderate posts from @clary and other regular contributors to the HE Board. But for my own reasons I join the consensus.
I have been assuming that DS is Y12.
In no particular order, here are some thoughts that have not been done to death above.
The Engineering course at Oxford is very well regarded but not specialised. In this sense Cambridge is indeed a better choice. The area is also full of tech companies and there is good potential for well paying summer employment.
If DS wants to earn during a gap year he will need to check whether each if his top choices permit this. It is slowly becoming more acceptable in STEM but many still do not.
You say DS could commute by car to Oxford in about an hour. If that is to the city, it is likely another 20-40 min to get where he needs to be. In very stressful traffic or a tiresome Park and Ride system. Plus parking fees! Now his commute is really more like three hours daily, which is very high on top of his long working hours.
Intercity train commuting has its own set of problems, and I write as one who knows.
You mentioned that living at home would be for later. But that’s when he is likely to have the most group work, and evenings are prime time for this. Also unless DS is teetotal -which about 25% of UGs are now - the need to drive home will severely affect his social life.
As a potential EE student DS may already be able to start earning. Perhaps this Xmas or sooner he could go into business helping people with their tech? I think even a HS pupil who is good with tech and reasonably personable and professional could easily command £20+/hr helping families to efficiently get their Xmas tech up and running.
Maybe do a couple of volunteer jobs for charities or even his school or college to get some good references first.
Southampton, where I don’t know CoL, Glasgow (where DS could likely do Y2 entry), Lancaster and Sheffield all have top EE programmes and CoL at the last three is quite reasonable, particularly at Sheffield. Leeds is also very good but perhaps a bit more expensive (?)
EE is a more stable field than many areas of tech with excellent prospects. I would support DS to the full extent practicable for your family circumstances. If DS is particularly concerned about employment, a degree programme offering a year’s industrial placement may be worth considering.
No matter where DS ends up I would expect him to be able to work during the summers.
Best wishes to him