There used to be a loophole in student finance, where if a child was at university at the same time as one of the parents, then that parent was treated as a single individual and none of the family income taken into account. I remember it, because of a case that was a tad annoying - incredibly rich family, where the mum was doing a fine art degree and entitled to full loans and (at the time) grant, despite the husband being on plural hundreds of thousands a year. Other families, with one spouse doing a degree and young children, got far less, because the working parent's income was taken into account.
It may well have changed, as this was an awfully long time ago, but if your youngest is 17, and is planning to go to university as well, then it may be worth investigating? You could be markedly better off.
I wouldn't do an OU degree, personally. As has been said, you miss out on the academic peer interaction, which teaches you so much in itself. And I'd have a hard think about what you want to do with the degree, at the other end, and what would serve you in achieving that career aim.
@Theoldwrinkley, you do not need an apostrophe for sons, and sentence fragments are not grammatically perfect useage, either. And while your inverted commas around 'sword of Damocles' were redundant, the correct capitalisation of the proper name would not have been.
Many of us are lax when posting on Mumsnet. That need not reflect our ability when writing more formally, as I'm sure you will agree.