YSK: you may be able to add your children as authorized users on your credit cards.
Why YSK: Some banks have no minimum age for authorized users, and report credit usage for them. If you have a credit card you don't use much, you can add your kids as authorized users, set up a reoccurring payment from the card and an automatic payment to the card, and then forget about it. Your kid could become an adult with an already-maxed credit score.
My parents did this when I was in college, and I used the card to pay for tuition and books. Yes, I was incredibly lucky to have my parents pay for everything.
Because I was an authorized user on my dad’s Amex he had had for decades, my credit history is technically older than I am.
As OP mentioned, this helped my credit score a lot. If you’re able to do this, it’s a huge help down the line.