Here are some simple songs that my kids love. They are basic and can be sung by those who know limited Vietnamese.
1) "Look at the Yellow Butterfly".
The lyrics and words can be found here.
2) The basic pat-a-cake recitation:
Vỗ tay, vỗ tay. Bà cho ăn bánh. Không vỗ tay. Bà đánh trên đầu.
Here is a good example on Youtube of a child doing this. Has anyone found the lyrics questionable? The words literally go like this:
"Clap your hands, clap your hands. If you don't clap your hands grandma will hit you on the head."
The kid and not the parent, of course, claps himself on the head at the end of the song. My son likes to replace the word "đầu" or "head" with different objects.
Vỗ tay, vỗ tay. Bà cho ăn bánh. Không vỗ tay. Bà đánh trên .... [replace with another object or body part].
He goes nuts over this. He points to houses, cars, his nose, his belly, his little brother, etc., and waits for me to name them in Vietnamese.
"Clap your hands, clap your hands. If you don't clap your hands grandma will hit .... the cactus!"
Have fun teaching your kids new Vietnamese or English vocabulary as you sing this simple song. :)