We performed a very simple version of Cinderella this summer. The children ranged from ages 6-9 years and with varying abilities of English.
I recommend keeping the script very short, preferably using simple phrases and ensuring that each child has a “line” to learn and recite. If you have a very large class or very young children making it more difficult to allocate lines individually you could consider creating a “chorus” that acts and speaks together. We accompanied Cinderella with a chorus of little helpers in the form of cats and mice. Why not also try doubling up characters. We performed our show with Cindrella A. (in rags) and Cinderella B (in riches) AND by doing so it enabled more than one participant to play the much sought after part!
To accompany your “show” I suggest you also include some songs , rhymes or poems. Children love to sing and dance and it will make rehearsals a lot more fun and help children focus if you can break up acting scenes with some musical interlude. We even managed to perform “Dancing Queen” to the delight of the children and admittedly also myself.