You need a medical detox by sounds of things.
I know there’s a fear around going to services but you should contact local drug services for their help and support.
they may involve children’s services but only for support and if you are engaging with treatment you won’t risk losing your children.
surely that’s better than killing yourselves.
so sad to hear how trapped you feel in your addiction and as a mother it’s so scary for you. There is help there.
if you feel nervous about going to a service then go to a NA meeting I’m sure there will be others there recovering from opiate addiction and be able to offer advice and support.
good luck xxx