As parents, it is our job to help our children to prepare for adult life. If they're going to be fully prepared to function as adults, they'll need to know how to create a budget, and how to stick to it. Your children will be happier, healthier and wealthier if they are able to learn these skills from you.
Talk to your kids about how to plan a budget. You can use your own expenditure as an example. Sit down together and make a list of all the things you need to pay for over a month, then over a week. The act of doing this will set a great example of how to get started, and children will find it fun (and surprising!) to work out how much you're spending. Getting them actively involved will mean they learn more, and understand that money isn't an endless commodity, it has to be carefully divided and eked out when needed.
Write down what you spend your money on every day. The children will appreciate how much things cost, and will learn to document their own spending. If they are given pocket money, ask them to note their purchases. Encourage them to conduct regular reviews of their spending, and think about whether some purchases could have been avoided or swapped for cheaper alternatives.
Teach your children to operate with cash. Show them to withdraw the cash they need at the start of each week, and only spend what is affordable. If you only ever pay for things with cards, your children might not have a clear understanding of the real value of money and the cost of things.
The key to educating your children about anything, including managing money, is talking to them. Use words and real life examples that they can understand, and show how budgeting works in your own household. Doing this can help children to become financially sophisticated adults, and help you to avoid a lifetime of worry!