Thank you for everyone who voted. The two most popular prototypes were the concertina screen, and the slot together house. From the feed back i received i have decided to create a combination of the both of them. A slot together screen. This can also be then be taken apart, and the children's own creations can be made. The life size version will have completely closed gaps.
On one side of the screen will have a fantasy map designed by me, for the children to use their imaginations. I am thinking of creating some kind of character, interactive feature that will encourage this.
The other side will be left for the children to create their designs on, to encourage creativity. Here are a few of the slot together designs i experimented with.
Its a shame as foam board was perfect for this, waterproof, light and fairly sturdy but unfortunately it cannot be laser cut as it is made of PVC. I created a more life size piece which shows the gaps closed.