Child visitation question

If both parties sign a hand-written (or typed) agreement and have it notarized, will this hold up in court at a later date should one party decide to contest it?

If not, is there a free child visitation mediation service in NC, or would I actually have to hire a laywer?

A separation agreement is enforceable in court, however with respect to custody it is better to have any agreement entered as a court order as court orders are more difficult to change, and easier to enforce.
Many counties do offer, and require, that parties to a custody lawsuit attend mediation for child custody and visitation, however a lawsuit must be initiated before this service is available.