... They are 7.... Jesus!
Yep, and good money management, like all of life skills, starts young. Unless of course you want to propagate generations of codependent people.
It's not rocket science if a 7 year old can't go through a few numbers and tell you which one has the highest interest rates you want to stop the saving for their future and start putting some serious time into their educational standards.
If you can't explain that money in the bank can't be physically stolen but is protected by the government to a certain value per institution then really how the hell are you going to explain other more expansive topics to a child.