An agreement reached by the parties as a result of mediation shall be limited as follows:
(a) Where mediation is required to settle a contested issue of custody or visitation, the agreement shall be limited to the resolution of issues relating to parenting plans, custody, visitation, or a combination of these issues.
(b) Where a stepparent or grandparent seeks visitation rights, the agreement shall be limited to the resolution of issues relating to visitation.