re: Treasury notes

There is a major problem with this approach.

You need to find a monetary instrument that outpaces inflation. Typical inflation is 2.5% - 3.0% a year. College tuition inflation averages around 8% per year. If you aren't averaging that kind of return, you are essentially losing money as it relates to purchasing power. In this case, the purchase is tuition.

I'd recommend a very stable, low cost mutual fund if you are risk averse. One that focuses on low volatility, consistent dividends to reinvest and preservation of principal.

Otherwise, you are at risk from an angle that lots of folks don't consider. Purchasing power or interest rate risk.

Good luck.