What about ‘kids cards’? My proposal is additional Monzo cards attached to my account which I could give to my children and I could put money into via the ‘pots’ system. That way I could give them an allowance and make sure their money is not being misused. When, they’re old enough they can apply for their own account and card.
There are kids accounts available with other providers that utilise cards, but this is more of an allowance system for younger children, to teach them about money and to make sure it’s not being mishandled.