Under Oregon Statutes § 108.710:
Subjects of agreement; child support not to be adversely affected.
(1) Parties to a premarital agreement may contract with respect to:
(a) The rights and obligations of each of the parties in any of the
property of either or both of them whenever and wherever acquired
(b) The right to buy, sell, use, transfer, exchange, abandon, lease, >
consume, expend, assign, create a security interest in, mortgage,
encumber, dispose of or otherwise manage and control property; (c)
The disposition of property upon separation, marital dissolution,
death or the occurrence or nonoccurrence of any other event;
(d) The modification or elimination of spousal support;
(e) The making of a will, trust or other arrangement to carry out the
provisions of the agreement;
(f) The ownership rights in and disposition of the death benefit from
a life insurance policy;
(g) The choice of law governing the construction of the agreement; and
(h) Any other matter, including their personal rights and obligations,
not in violation of public policy or a statute imposing a criminal
(2) The right of a child to support may not be adversely affected by a
Marriages may be terminated only by death or court order of divorce or annulment, so one can't get divorced without going to court.
Furthermore, the right to seek a divorce may not be waived entirely in any state, although some U.S. states have a concept called "covenant marriage" that can subject a marriage to fault based standards for divorce rather than the no fault standards that apply otherwise (the applicability of those laws if divorce is sought in another state is something of an open legal question). An agreement to do so would be void as contrary to public policy.
In general, marital agreements pertaining to child custody and child support are void because the children are not parties to the agreement.
Matters that are properly within the scope of what may be in a marital agreement can, however, generally be required to be resolved by arbitration. But the marital agreement and arbitration awards arising from a marital agreement cannot be unconscionable as applied even if they would have not been unconscionable, necessarily, when entered into by the parties. See Oregon Statutes § 108.725 which states:
Party may prove agreement unenforceable; when court may require support; determination of unconscionability.
(1) A premarital agreement is not enforceable if the party against
whom enforcement is sought proves that:
(a) That party did not execute the agreement voluntarily; or
(b) The agreement was unconscionable when it was executed and, before
execution of the agreement, that party:
(A) Was not provided a fair and reasonable disclosure of the property
or financial obligations of the other party;
(B) Did not voluntarily and expressly waive, in writing, any right to
disclosure of the property or financial obligations of the other party
beyond the disclosure provided; and
(C) Did not have, or reasonably could not have had, an adequate
knowledge of the property or financial obligations of the other party.
(2) If a provision of a premarital agreement modifies or eliminates
spousal support and that modification or elimination causes one party
to the agreement to be eligible for support under a program of public
assistance or medical assistance at the time of separation or marital
dissolution, a court, notwithstanding the terms of the agreement, may
require the other party to provide support to the extent necessary to
avoid that eligibility.
(3) An issue of whether a premarital agreement is unconscionable shall
be decided by the court as a matter of law.