Learn about the condition, familiarize yourself with the terminology. Don't let your health, emotional and physical, suffer as a result of the stress you may feel under. Express your emotions and don't bottle it all up. You can gain strength from so doing and not feel it to be a sign of weakness. You are the first and greatest influence on your child's life, and that is the greatest responsibility you will ever carry.
Children are very curious people.
They ask direct questions, and if given reasonable answers think nothing more about it. If you give your child a reasonable explanation about the condition, one that they can tell their friends, then teasing and name calling can be reduced. Do not deprive your child from social interaction, and indeed you should encourage mixing with other children from an early age so that your child can learn to handle different situations, and so that other children too may readily accept your child as they would any other. Because a cleft lip is such an obvious physical condition, your other children may at first be scared and apprehensive. They may also become jealous of the amount of time and attention you are giving to the new arrival.