Oh gosh belfie, i was going to come in and offer advice, but you have done and tried everything.
The 'best' moisturiser for my DS has turned out to be a natural colloidal oatmeal one. (Aveeno). So we do the colloidal creamy wash in the shower (pfft bath - not happening here!), and then the eczema cream and them the colloidal oatmeal moisturiser.
Also i bought a 100% silk duvet inner. Seems to help him not get too hot and irritated at night.
I know this all costs money and there are no guarantees it will work for your kids.
I'm sorry you have to deal with this. Sounds more than 'mild' to me.