We teach our kids how to stay healthy, stress the importance of good grades, help them with schoolwork and even tackle the awkward topic of sex (gulp). But according to Beth Kobliner, author of Make Your Kid a Money Genius (Even If You’re Not) (Amazon $9.99), parents aren’t talking with their children about an important topic: money. And that reticence can hurt our kids in the long-term, because they’ll enter a complicated world without the necessary financial literacy.

Don’t panic, though. Even if your children are older, it’s not too late to give them the tools they need to be “money geniuses,” Kobliner promises. We spoke to her recently about her best-selling book, which is full of practical money advice for a range of ages. So whether you have a preschooler at home or a soon-to-be-adult still under your roof, Kobliner explains how to talk to your kid about saving, staying out of debt and being a smart consumer.

Kobliner told us she hears from readers from a range of backgrounds, regions and financial situations, but they all want the same thing: to make sure their families are okay. “People are feeling uncertain right now,” Kobliner says. “Anyone who has kids loves their kids and wants to help their kids be financially secure. I hope I made a compelling case in the book that even if you are terrified of money, or you are embarrassed about money or ashamed about your money past, you have to put that aside and focus on teaching your kids. There are things we can do to help our kids, and it’s not that hard.” (We love this very reassuring paragraph in Kobliner’s book: “One of the best-kept secrets in the world of personal finance is that there are really only a few concepts that matter. The smartest, most financially successful people understand this.”

Parents also tell Kobliner that credit and debit cards are making it far too easy to spend and far too hard for kids to realize that the old adage “money doesn’t grow on trees” is true. She spoke with parents of college-age kids whose children left for college and were given debit cards with small amounts of cash on them to pay for extras. In three different cases, the kids called home upset saying their “accounts had been hacked.” But once they talked through all the things they’d done—going out to lunch with friends, taking a road trip, etc.—these “smart kids realized they’d spent all the money themselves. It hadn’t registered that money was being used for all these activities and purchases.

Before you roll your eyes, realize that all of us find it easier to pay for things using a “magic card that … takes care of everything” instead of going to the bank, taking money out of our account and handing that cash to a retailer, Kobliner says. Her takeaway is to be very clear about spending. “Use cash,” she says in her book. “I can’t stress this enough. Spending cash is more ‘painful’ than putting down plastic.”