The children may bump into one another or you will not have enough room for your audience. If your space is too big it could have a terrible echo, the children could stand too far apart creating a problem with your stage blocking. Props are very important in a stage production. They can be very large and extravagant or very small and simple. Props are not always necessary.
Actors can act as though they are holding different objects or sitting on chairs and so on.
If you have access to the props needed in the production use them. They can give actors attributes for the characters that they are portraying. It is important to have someone such as an assistant assigned to the props. All props should be labeled with the name of the character and when it will be used during the play. As you read the play, you will decide where the actors should enter, exit and stand.