Singing a defined note is a basic skill that any child needs for success in a choir. Sing a note and have the entire choir sing it back to you. You can also try having students sing the note back to you one at a time. This way, you will be able to find which students have trouble with pitch matching. You can then divide the choir into two groups and give the less-skilled students remedial practice.
In addition to pitch, rhythm is a key skill that young children need to learn. Clap a simple rhythm and have students repeat it back to you. You can also sit in a circle and have students do the rhythm one at a time. Have students take turns being the "leader," coming up with their own rhythms for the rest of the choir to tap back. Make it more fun by switching up how the rhythm is played, such as by stomping feet or banging two sticks together.
A song with actions helps young choir-members remember a simple melody by letting them associate the words with movements. Songs such as "If You're Happy and you Know it Clap your Hands," "Itsy Bitsy Spider" and "Head and Shoulders, Knees and Toes" are simple songs that young children can have fun doing the actions to. You can also have students sing "London Bridge" while acting out the bridge falling down.
Once a preschool choir has developed enough experience and skill, have them perform a song or a group of songs for other students or for parents. If it is a song with a specific theme, you can have students dress in costumes relating to it. Have students practice standing straight, looking ahead at you and singing together in unison. Show them how to bow during applause and walk off stage in a line.