Ah, come on now OP. Whichever way you frame this you want to use money that was never intended for you, to maintain a lifestyle that is unsustainable on your current income.
Your DH does not want to use the money left to him for you to continue being a SAHP, he has made that clear by asking you to get a job, so you have two options:
a) cut your cloth and live within your current means; or, b) get a job.
Your reasons are far too wishy washy, all I can hear is 'but I don't waaaaant to'.
I don't want to fritter away their inheritance but I think the disruption to them of me doing more hours is more harmful than borrowing some money now that I can give them back in a few years when I'll be able to do more hours. No. If they are at primary school you wont be disrupting them, it will be a couple of hours max per day like god knows how many kids is not going to harm them, thats bollocks. And 'borrowing' from savings/lump sums for living expenses is a bad idea as it means you can't afford to pay it back!
I have my own issues. My own mother was disabled and always at home until she died when I was 18. I am terrified of childcare and desperate to avoid it for my kids. Yeah, well I got stung by a bee when I was a kid but I don't shit myself every time I see a garden. Why in god's name would you be scared of childcare? You do realise you get to pick who looks after the kids, dont you? They don't randomly allocate an ogre. Plus your kids are not babies, they are primary school age, they're capable of telling you if they hate it.
There's just nothing you've said that could possibly justify spending money that wasn't meant for you in the first place on living a lifestyle you can't afford.