I have read a few things in this post that are just plain wrong in the U.S. Bear in mind that I am not an attorney, but I do teach Business Law at the college level, so I try to stay up on contracts to some degree.
You can enter into a contract with a minor, and the courts will force you to honor a contract with a minor, but the court will not force the minor to honor the contract. That is the long and short of why you do not enter into any kind of contract with a minor in the U.S.