Set up automatic payments so they are initiated on your end, so that you send out money to the bill/ company you’re paying instead of giving them access to take money out of your account.
Have a yearly “review” right before school year. Raise allowance as appropriate. If they want more money, they’ll have to take on more responsibilities.
Start “home economics” school with them. Laundry, cleaning, cooking, how to change a diaper, comfort a baby, soothe a toddler, what's involved in caring for pets, budgeting for food, keeping track of maintenance schedules for humans, pets, cars and machines. Engage with guests, be a good host, etc. Know when and how to tell someone to GTFO of the house (racist or misogynistic speech, etc.) Every kid needs to learn the art and science of home management. Look for and point out examples in books and movies of good home science skills.
Practice “going without.” Talk about how nobody gets what they want all the time. We should learn how to just choose to go without something we want. Get them in on the discussion and pick something every day to do without.
Work on developing a “no shortcuts” mode. Looking for a faster/easier/bare-minimum option isn’t always bad. People get paid a lot of money for creating efficacy. But there are times when that approach is wrong. Anything you want to grow from (relationships, school, work, wealth, health, knowledge, etc.) those things deserve your full effort, focus and dedication. Play. Definitely play! But don’t f*ck around.
Check out from the library or Amazon: “My First Money Book: A Guide for Parents and Children to Saving, Spending, Sharing, and Investing Your Money” by Reggie Nelson
It’s fine, great, to be thrifty. But please don’t be cheap. Hard-earned money should neither be squandered or hoarded. Enjoy your success! But save more than you’re comfortable with. It’s like my running coach used to say: Keep going until you feel like you’re gonna poop your pants, then push yourself to do another mile. Point is, it should hurt a little.