What is "too young" to get a credit card, these days? I suspect I was 16 or 17 when I got one, likely coinciding with the need to buy gas.
I should have been more clear, we did add our kids as authorized users to our oldest credit card when they were children just to establish their credit. It works great. The children don't even have to know you did it but be sure you don't screw up and ruin your kid's credit. My father did this for me before I was even a teenager.
When my kids were of age to buy books for college they use the credit card and give it back to be placed in the safe when done. Before they are 18 YO of course.
The kids use a debit card attached to their bank account for buying gas and other children things like candy bars with their money.
After they turn 18 they could, but have not, gotten their own credit card. The companies certainly offer CCs to the college attending daughters with excellent credit.