Riven: you should tell them to go. No question.
From your posts about them, they sound bright. DD1 is off to Cambridge, right? Your DSs are aiming for RG universities, yes?
There is every chance, Riven, that your DC will be able comfortably to pay off their loans, etc., with that kind of university education behind them.
And what will they do if they don't go? Yes, there's a chance they could work their way up in any given industry. But it might also mean that they miss out on the careers and open doors which a degree leads to. You, more than anyone, should acknowledge that a lifetime on a low income, even if not saddled with debt, could be harder than one with the promise of a better income ahead.
Incidentally, I know several research scientists who earn more than that. A good friend is a cancer research specialist, and she earns nearly 50K, and she's not even a professor. I think it depends on the institution, or specialism.
Also, if your DS decides to become a lecturer in science, rather than a researcher, most universities now have an entry level salary for lecturers of 35K or more.
Scientists working in industry can earn even more. A friend worked for Rolls Royce, and earned plenty!
Another friend studied science, then moved into science & patent law. Again, earning a very very good salary, with sky-high salary opportunities ahead.
Another scientist friend lives off the revenue generated by his patents! He is my age - early 30s. Not bad, eh?
There is LOTS of money to be made by the scientifically minded. Lots and lots.
I understand that the levels of debt faced are frightening. But students with brains and motivation should do well in life, and manage to repay a debt (particularly one that doesn't attract interest at commercial rates) reasonably comfortably.