In general, a contract does not need to be notarized or witnessed to be binding. (Of course there are exceptions, such as those imposed for wills, for recording real estate documents, and possibly, involving divorce arrangements.) But for most contracts, we do not generally require them to be witnessed or notarized, to be "legal." The notary removes the issue as to the identity of the parties signing the contract. But, it is not usually a prerequisite of a binding agreement. Oral agreements are also generally binding (with some exceptions, such as contracts relating to the debts of another, real estate, or promises that will take over a year ro perform), but sometimes hard to prove. It may be that as a matter of the family law in your state, the agreement must be notarized or witnessed. Otherwise, it is up to the intent of the parties. Your family law lawyer should help you on this. If you don't have a lawyer helping you, I assume the amount involved with the contract doesn't really justify that expense.