When child support is a part of divorce, if both parties agree on an amount, is it a req to complete the form to figure amount?

My husband and I are getting a divorce after 24 yrs of marriage. We have a 13 yr. old son and a 21 yr. old daughter. We are discussing the terms of the divorce to complete an uncontested one. We have agreed on an amount for child support. Do we still have to complete the form to figure support amount or can we advise the court of a pre-agreed amount?