Moisturiser for eczema

The moisturiser will just keep the skin soft and make the eczema less uncomfortable.
Only steroid will get rid of the flares. But do not overuse it because the skin gets used to it and the flares are worst/come back when you stop. It also damages the skin long term.
Use the steroid if the flares become really bad but no more than a week and put plenty of emollient/moisturiser.
I use Epimax most of the time but I also like hemp oil and shea butter.

Be very generous on the emollient. And use it after shower, washing hands etc.

Also make sure the air is not too dry. Around 50/60% humidity.

I second what Fatima already said. Steroids work wonders but in small doses, I was hospitalised 2 years ago for topical steroid withdrawal because of using them since childhood. Don’t be too scared though because this didn’t happen for me until adulthood and using very strong steroids because my eczema was out of hand and being treated by GP and not dermatology.
Epimax is great, cetraben works too. The “greasier” the cream is the more hydrating so try a thick layer of ointment and put them in long legs/long sleeves fitted dark clothing to seal the moisture in overnight (can also use gloves and socks for hands and feet), ideally use cotton where possible. I have prescribed pyjamas called skinnies which are essentially leggings and a long sleeve top to layer on top of my ointments.
Aquaphor healing ointment is good over the counter.
You should be able to be prescribed a soap alternative instead of body washes/soaps but if you can’t try and cetaphil gentle skin cleanser from boots.

You could also try oat baths (oats in a bag seeped into bath water- give it a google) or Oilatum Moisture Rich Bath Soak.
Dead Sea salts work best for me in the bath (I use half to an entire bag per bath) BUT it is painful to get into so I wouldn’t recommend for little ones.
You can also buy a cream on Amazon called Udderly Smooth (in a cow print tub), it is pricy but was recommended to me as a teen by a GP and was helpful.

Do your children have any allergies or intolerances? Quite often, eczema can be a symptoms of an allergy or intolerance, the most common one being dairy