This has been a proper treat hasn't it?
You don't want to teach because you want to see your kids (unlike everyone else of course, who hate theirs)
You don't take a job because your husband is "protective" of your CV (what does that mean exactly, when doing NOTHING is apparently better than doing anything at all?)
You think your kid will get into Eton when he can't even get a small scholarship for the local school
You think your kids are the only ones in the whole world who understand quality, and that without rolling lawns etc they will simply DIE
It's a shame, you know, because your kids sound bright and sweet. But what you're doing to them is making them think that private schooling has a value in and of itself. In other words, that EXPENSIVE things are better, just because they are. That free things that are available to everyone are less worthy, exactly because they are available to anyone. So if they can enjoy a state school where they have normal lunches without anyone playing the lute over them they must be worth less too, reduced to the level of those who don't "understand quality".
I went to a top university and have friends from all backgrounds (I'm state educated). The only advantages my privately educated friends appear to have are those that come from huge family wealth, on which they are able to fall back, or which can help them buy a house etc. I.e. not the results of their private education, but the thing that enabled it in the first place.
But then the reason many have needed to fall back on this money has been because they haven't all found good jobs, or started earning high wages, despite all their advantages and their insight into holiday homes... Some of them want to be writers or actors and don't NEED to pay rent because of parental support, so carry on trying ad infinitum. Some of them took too many drugs (because they are REALLY popular at private schools, where the kids can actually afford them in large amounts) and they lost all their motivation and just moved back home. I'm not saying this happens to all privately educated kids, of course, just that it happens to some of them like it happens to some state educated kids.
You're tying yourself in knots because you think if you can't privately educate your children, they will become snotty nosed low achievers who never even think about getting a job beyond their local town. I'm telling you now, their schools are not what will make this difference. You and your husband are obviously clever (in some ways at least!) and you will broaden their horizons, no doubt about it. Racking the family with worry and debt, and instilling your snobbery about private education into your children, really are the opposite of the gifts you want to give them.
There is a difference between raising aspirations, and making kids think that ONLY the best is good enough. What do you think will happen when one day they ask for "the best" and you have to tell them, no? If no sooner it will come at university when they want to live in the warm, pretty accommodation and - you sticking to your promise - tell them to busk until they have enough to live in the concrete block shack down the road. They won't understand it, how could they?