That is a great idea!
Other ideas: Tell the kids right up front (say, about sophomore year of high school) the fixed amount you are willing to pay and for what time frame. Whether it is $50,000/year for 8 years or $10,000/year for 4 years, be sure they know what you are willing to put on the line, so that they will own any decisions that require them to take on debt.
Help them see the “cost” of going longer than is really needed, and the “cost” of going for degrees that are worthless. At one point my daughter thought she might not graduate (BSN/RN) in 4 years. I showed her that one more year of college would cost X for more school expenses PLUS Y for the lack of income at her occupation for that extra year; which made it more than twice the “cost”... about a week later, she had met with an advisor, and they worked out a plan that kept her on track for the 4 year graduation.
Be sure they understand the “cost” of taking student loans that will end up just financing a party or frivolous lifestyle while in college. The extra $100 or $300 per month, borrowed now to allow for plenty of pizza and beer, turns fairly daunting when amortized for the 10 year repayment plan, with interest....
Consider deferring borrowing as long as possible and/or making some interest payments while the kid is still in school; will keep the interest from compounding the first 4 years or so.
Do what I did...WORK!!!
I was a waiter in college, I made a killing especially on football weekends.
And employers will want to know how you financed your education.