You can find a lot of examples of that stuff on youtube I think. For the song, get or help the kids make some kind of costume or prop then work out a very simple dance routine. For example do the monkeys jumping on the bed song. Have them wear mokey ears and tails from Daiso. Then they hop around and sing until one of them is left.
For the short play I would a fairy tale or fable. Something you can edit to make easier for them and still complete the message of the fable. 3 littel pigs comes to mind.