Well. At least the kids'. I had the problem of kids getting money from birthdays, chores, and other random things and keeping it. They would leave it lying around, then we couldn't remember how much was there, did we pay tithing on it . . . you get the picture.
I came across this idea on another website - "meckmom.com". It looked cool, so I tried it and it has been working wonderfully. I definitely recommend this to any parent who has the same problem as me.
I got a binder.

I bought a pencil case for each child to put their money in.

I made up a record sheet so that each child can keep track of their monies.

I had to be willing to get out the binder whenever the kids wanted to use their money, that way, they felt that they had some control over their money. I think because of that, this idea has worked. I try to get them to fill out the sheet whenever their are taking or depositing money. When they save up so much money, then I will take them to the bank to deposit their money.
Next task ----- BUDGETING (cue the scary music).