re: Treasury notes

I think what you're actually wanting to look at is called treasury strips or zero coupon bonds. They're usually bought at deep discount and mature at par value, the owner would pay a phantom income tax however.

These are kinda an old way of funding a specific goal for something in the future with a lump sum. But since you mentioned your adding to this monthly, you may wanna check out some different investments within a UGMA/UTMA or 529 account. Depending on what you specifically want the money to do.