Taking every opportunity to share the importance of money management with your children is never a discussion to miss. Teaching kids the importance of handling money well with a biblical perspective will instill a great foundation early in life. One way we started teaching our kids was by giving them opportunities to work hard and make money. The bigger the project the more we paid them. Not only does this instill good work ethic, but it also helps them to get started in handling money. When they first earned a little cash, we taught them to have envelopes for tithe, savings and spending (The spending cash of course typically goes right into their wallets). Teaching them that no matter what amount they earn, tithing is always first, saving is second and spending is last. It has worked well for us. But, however you choose to teach your kids God's principals on money management, just remember they are never to young to learn that our money belongs to God and we're merely stewards of it.
Here's a fun tip: Give your kids white envelopes to decorate with stickers, markers and paper. Then have them label them what they are for (ie: tithe, savings, spending). This might get them excited and may open the door for you to start sharing the importance of money management.