Dear Lovekidslovedogs
Another option you could look at is
https://www.roostermoney.com/. It is a little different to the prepaid card options but can be used to discuss saving rather than/or in addition to spending.
I manage the Killik & Co branch on the Northcote Road and we are always on the look out for ways to explain what we do. One idea we are keen explore is working with the next generation of savers and investors to explain the value of saving a little bit regularly and how powerful it can be over the long term.
If you ever need any help explaining different financial concepts to your children please pop in and I'd be delighted to help if I can.
Best Wishes and Merry Christmas
Richard